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IBM XIV Thin Provisioning and Space Reclamation

1. XIV Volume 1 e XIV Volume 2 Type Local Disk Type Local Disk File system NTFS File system NTFS a Used space 33 742 848 000 bytes 31 4 GB i Used space 67 323 363 328 bytes 62 6 GB Free space 568 407 097 344 bytes 529 GB B Free space 534 826 582 016 bytes 498 GB Capacity 602 149 945 344 bytes 560 GB Capacity 602 149 945 344 bytes 560 GB Drive F Allow files on this drive to have contents indexed in addition to Allow files on this drive to have contents indexed in addition to file properties file properties Apply OK Cancel Apply Figure 5 7 Volume size after moving files The XIV GUI indicates the new volume capacities as shown in Figure 5 8 Size GB Used GB Consistency Group e ITSO O 309 0 GB Hard E vol 001 602 GB 33 GB E vol 002 602 GB 67 GB Figure 5 8 Volume capacity after moving files Chapter 5 Space reclamation with XIV 39 Snapshot behavior If you take a snapshot of Volume 2 and then move the files to Volume1 the same reduction in allocated space occurs as shown in Figure 5 9 m Size GB Used GB amp ro amp vol_001 amp vol_002 Figure 5 9 Volume capacity allocation o The Storage Pool does not show any Snapshot space allocated because there have not been any updates to the files as shown in Figure 5 10 Snapshots GB Figure 5 10 Pool capacity allocation However after the f
2. gt Pre allocating for future requirements It is a common practice to pre allocate storage space for the application based on future requirements This is because resizing volumes is a difficult and time consuming IT operational task for both storage and applications gt Over estimating needs Storage space allocation is typically based on a prediction of future use If this prediction is inaccurate and the allocated storage goes unused there is no practical way to reclaim the allocated storage for other applications gt Full copies of unwritten data Many application needs such as testing and data mining require copies of the original data either at the application level file copy and so on or the storage level snapshots and full copies Traditional architectures copy both used and unused data thus increasing the amount of unused space These reasons help explain why storage one IT s most expensive and complex resources is underutilized to a large extent The cause is not inappropriate management practice but the very nature of the pre allocation of storage and the inability to easily reclaim this storage if it goes unused The real cost of unused storage Although unused storage is itself costly there are many additional hidden and indirect costs gt Capital expense You can reduce the direct capital expense of storage by purchasing only the storage required for actual usage For example if you have a storage pro
3. Ensure that system storage pool alerting is set up and working Test storage pool alerts on a regular basis Practice how to respond to storage pool alerts Have escalation rules in place Set pool alert thresholds no higher than the system defaults Warning 80 Minor 90 Major 95 Critical at 95 This is not a system default but is recommended for thin provisioning Follow these typical steps toward thin provisioning practice maturity Decide that thin provisioning is a storage provisioning policy option that you want Choose one or two XIV system storage pools to use to become proficient with thin provisioning Ensure that these storage pools do not contain business critical production applications Become familiar and comfortable with managing and monitoring thin pools Implement thin pools as a storage allocation option for new projects Consider asking IBM to expand the total system soft capacity beyond the total system hard capacity when your XIV system allocated soft capacity approaches the total IBM XIV Thin Provisioning and Space Reclamation system hard and soft capacity Typically this new system soft capacity is set at 50 over the hard system capacity Have a contingency plan As system hard capacity approaches 80 you need more storage or high priority intervention to alleviate this situation Add modules Delete snapshots Migrate or mirror data to another XIV
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5. This utilization requires that the aggregate space available to be allocated to hosts within a thinly provisioned storage pool must be defined independently of the physical or hard space allocated within the system for that pool Thus the storage hard pool size that is defined by the storage administrator limits the physical capacity that is available collectively to volumes and snapshots within a thinly provisioned storage pool The aggregate space that is assignable to host operating systems is specified by the storage soft pool size The XIV System Management GUI will not allow the hard pool size to be decreased to a value less than the current amount of pool hard data Regular storage pools segregate the hard space reserved for volumes from the hard space consumed by snapshots by limiting the soft space allocated to volumes However thinly provisioned storage pools allow the totality of the hard space to be consumed by volumes with no guarantee of preserving any hard space for snapshots Chapter 2 Thin provisioning in XIV 13 14 Logical volumes take precedence over snapshots and can be allowed to overwrite snapshots if necessary as hard space is used The hard space that is allocated to the storage pool that is unused the incremental difference between the aggregate logical and actual volume sizes can however be used by snapshots in the same storage pool Careful management is critical to prevent hard space for both logical vol
6. gt Determine application hard data storage and snapshot growth patterns as a part of the decision to deploy in thin pools Monitor the storage pool used capacity size and snapshot used size until a monthly growth trend can be determined As a rule the used size has a general linear growth percentage The snapshot used size likewise has a growth component After you know the storage pool growth patterns determine how far into the future to project growth This can be months or years This projection will be the hard size of your thin storage pool Determine that the application is appropriate for thin provisioning This is usually a consensus decision that includes the application owners The most important enterprise applications are not the first choice for thin provisioning Test and development environments are usually good thin provisioning candidates Storage pools typically contain a single application If the application is appropriate for thin provisioning it is easy to change the single pool from regular to thin provisioning Thin pools typically maintain a ratio of the pool soft size that is equal to 1 5 2 0 times the pool hard size In addition implement these processes to improve your success gt Keep snapshot sizes around 10 of the hard pool size unless observed growth patterns indicate larger snapshot areas are required Monitor XIV system thin pools carefully It is best to stay ahead of the alerting mechanisms
7. 407 228 416 bytes 529 GB Capacity 602 149 945 344 bytes 560 GB Capacity 602 149 945 344 bytes 560 GB Allow files on this drive to have contents indexed in addition to Allow files on this drive to have contents indexed in addition to file properties file properties OK Figure 5 5 Volume size after deleting files The XIV GUI Volumes by Pools display indicates that Volume 2 hard capacity has also been reduced to 33 GB as shown in Figure 5 6 Size GB Used GB Consistency Group e ITSO 309 0 GB Hard t vol 001 t vol 002 Figure 5 6 Volume capacity after deleting files 38 IBM XIV Thin Provisioning and Space Reclamation Note The space reduction occurs after the actual file deletion so there can be a delay of up to 30 seconds before the reduction in hard capacity is seen Moving files Moving data between volumes follows a similar process When the data is moved the capacity of the source is reduced and the capacity allocated on the target volume increases If you move files from Volume 1 to Volume 2 the Volume Properties panel displays the new allocated size as shown in Figure 5 7 XIV Volume 2 F Properties x Shadow Copies I Previous Versions Quota Customize Shadow Copies Previous Versions Quota Customize General Tools Hardware Sharing Security General Tools Hardware Sharing Security
8. 438 GB Bl Used space I Free space Capacity 602 149 945 344 bytes 560 GB Drive F Allow files on this drive to have contents indexed in addition to file properties OK Cancel Apply Figure 5 3 Initial volume size Chapter 5 Space reclamation with XIV 37 The XIV GUI displays the volume capacity also showing 67 GB capacity as shown in Figure 5 4 Ojo ame We ed GB onsiste mm e ITSO am 309 0 GB Hard E vol 001 602 GB 67 GB E vol 002 602 GB 67 GB Figure 5 4 Initial volume capacity Deleting files When you normally delete files the actual space allocated on the XIV system does not change However with space reclamation active the UNMAP command will identify the unused space and the XIV storage system will indicate that the volume allocated size has decreased After you delete files on Volume 2 the Windows Properties menu indicates that 33 GB is now allocated as shown in Figure 5 5 XIV Volume 1 D Properties Shadow Copies Previous Versions Quota Customize Shadow Copies Previous Versions Quota Customize General Tools Hardware Sharing Security General Tools Hardware Sharing Security d 7 XIV Volume 1 1 gt Type Local Disk Type Local Disk File system NTFS File system NTFS Used space 57 323 494 400 bytes 62 6 GB a Used space 33 742 716 928 bytes 31 4GB B Free space 534 826 450 944 bytes 498 GB E Free space 568
9. cannot be used by other storage pools Chapter 2 Thin provisioning in XIV 11 12 In contrast a thinly provisioned storage pool is not fully backed by hard capacity meaning that the entirety of the logical space within the pool cannot be physically provisioned unless the pool is transformed first into a regular pool However you can realize benefits when physical space consumption is less than the logical space assigned because the amount of logical capacity assigned to the pool that is not covered by physical capacity is available for use by other storage pools Add Pool Select System ATSXIV 1310115 3 ec Regular Pool D e Thin Pool e Hard 33 418 GB Q System Allocated 5X 1 Pools 42 I 137 889 GB o Soft 33 418 GB Pool Hard Size 33418 GB Pool Soft Size 33418 GB Snapshots Size 3355 GB Lock Behavior Read only X Pool Name oe Figure 2 1 Define storage pool The virtualized XIV data storage architecture provides you with wide flexibility in the use of thin provisioning gt gt gt You can mirror volumes in thin pools There are no restrictions related to which part of the mirroring relationship has thin volumes You can move volumes from regular pools to thin pools and back again You can change pools from regular provisioning to thin provisioning and back again Figure 2 2 on page 13 shows a regular storage pool and a thin pool gt In the regular pool the hos
10. carefully planned and managed because new risks for storage availability exist when thin provisioning is deployed 6 IBM XIV Storage System Thin Provisioning and Space Reclamation The XIV system provides a thin provisioning architecture that is tightly coupled with advanced snapshot and snapshot management technologies With the XIV storage system you can achieve the following improvements gt gt gt gt gt Use thin provisioning to limit storage expenses to the actual capacity used Reduce required management resources and the operational expense of resizing volumes Limit the effect of thin provisioning to specific applications safe guarding your most critical applications from running out of space Get notifications on thin provisioning usage Reclaim capacity that is no longer in use With the XIV system you can easily deploy thin provisioning and manage it effectively resulting in significant storage cost savings in your enterprise IT environment Chapter 1 Thin provisioning overview 7 8 IBM XIV Storage System Thin Provisioning and Space Reclamation Thin provisioning in XIV This chapter provides information about how you can implement thin provisioning in the XIV system Copyright IBM Corp 2013 All rights reserved 2 1 Thin provisioning implementation in XIV To begin our discussion of XIV thin provisioning it is a good idea to start with some definitions Thin provisioning is a method for op
11. in Germany He joined IBM in 1983 as a Customer Engineer for large system clients After 10 years of experience with all large system products he joined the DASD EPSG EMEA Product Support Group in Mainz In 2009 he became a member of the XIV PFE EMEA Team He has more than 20 years of experience providing technical support for past and present high end DASD products Hank Sautter is a Consulting IT Specialist with Advanced Technical Support in the USA He has worked at IBM for 34 years He worked for 20 years in Tucson Arizona with IBM S 390 and IBM disk storage hardware and Advanced Copy Services functions His previous years of experience include IBM Processor microcode development and S 390 system testing while working in Poughkeepsie NY Henry s areas of expertise include enterprise storage Copyright IBM Corp 2013 All rights reserved vii performance and disaster recovery implementation for large systems and open systems He writes and presents on these topics He holds a BS degree in Physics from Texas A amp M Jim Sedgwick is an IT Specialist in the US He has more than 20 years of experience in the storage industry He worked for five years with IBM as a Printer Design Engineer after receiving his Mechanical Engineering degree from NCSU Jim s current areas of expertise include enterprise storage performance and copy services He writes and teaches on both subjects Thanks to the following people for their contributions to this
12. not the only advantage of thin provisioning An additional advantage is your ability to take an existing volume on an existing system migrate it to XIV storage and reclaim unused space requiring for instance only 30 of the original capacity XIV thin provisioning and snapshots The XIV architecture seamlessly integrates thin provisioning with snapshots The system automatically thin provisions snapshots using physical space only when a delta exists between the snapshot and the master volume or between subsequent snapshots of the same volume For more information about the XIV system s snapshot implementation and features see the IBM Redbooks publication IBM XIV Storage System Gen3 Architecture Implementation and Usage SG24 7659 1 2 3 Advantages and disadvantages of thin provisioning Thin provisioning is a central theme of the virtualized design of the XIV storage system because it uncouples the virtual or apparent allocation of a resource from the underlying hardware allocation Chapter 1 Thin provisioning overview 5 The XIV system implementation of thin provisioning provides the following benefits beyond those enumerated in The real cost of unused storage on page 3 You can dynamically increase or decrease capacity associated with specific applications or departments per the demand imposed at a given point in time without necessitating an accurate prediction of future needs Physical capacity is only committed t
13. storage pool Each pool has its own hard capacity which limits the actual disk space used and soft capacity which limits the total size of volumes defined Separating thin provisioning per storage pool is essential in limiting the effect of running out of physical disk space Thin provisioning management is performed per pool and running out of space in one pool does not impact other pools An example of this is when a data center has backup to disk and business critical applications running in its environment The backup to disk uses thin provisioning with 100 TB of logical volumes and only 50 TB of physical space Application XYZ a business critical application needs only 10 TB and thin provisioning is not used With a IBM XIV Storage System Thin Provisioning and Space Reclamation poorly managed thin provisioning implementation backup to disk storage potentially impacts the XYZ application Such a scenario is unacceptable Some applications are simply too important to exist in thin provisioned pools With the XIV system you can use two storage pools one for the backup to disk and one for the XYZ application The XYZ storage pool will have identical soft and hard capacities and thus never be locked as a result of running out of physical space Alternatively you can configure the storage pool used for the backup to disk application with thin provisioning that is with soft capacity larger than hard capacity and receive all the advanta
14. API implemented Using space reclamation The vxdisk reclaim lt diskgroup gt lt disk gt command to free up any space that can be reclaimed In UNIX you can reclain space as follows Reclaim by disk group enclosure or LUN using these commands as appropriate vxdisk reclaim lt dg gt vxdisk reclaim lt enclosure gt vxdisk reclaim lt da name gt By default the reclamation does not affect unmarked space which is the unused space between subdisks If a LUN has a lot of physical space that was previously allocated the space between the subdisks might be substantial Use the o full option to reclaim the unmarked space as follows vxdisk reclaim o full lt dg gt lt enclosure gt lt da name gt Reclaim by file system opt VRTS bin fsadm R mount point opt VRTS bin fsadm R A mount point opt VRTS bin fsadm R o analyze mount point opt VRTS bin fsadm R o auto mount point IBM XIV Thin Provisioning and Space Reclamation gt In Windows you can reclaim space as follows Reclaim by volume free space or both all C vxdg g lt DiskGroup gt reclaim option volumes freespace a11 Reclaim by disk C vxdisk g lt DiskGroup gt reclaim lt DiskName gt Note Thin reclaim operations are not supported on RAID 5 VxVM volumes on UNIX and Windows If your administrator wants to inhibit thin reclaim operations this can be achieved by populating a file etc vx
15. BM XIV Thin Provisioning and Space Reclamation Space reclamation with XIV Thin provisioning provides a volume size as specified but uses physical storage only when needed Although this sounds like a great way to use your available storage space efficiently in real life situations this might not always be true When files are deleted or moved the now unused data is usually still residing on the physical storage The host system might indicate that the used capacity is now smaller but the physical storage is still in use and remains allocated to that host system Space reclamation deals with this situation by providing a way for the host system to indicate that the physical storage assigned to it is no longer in use Various host operating systems deal with this process differently so the commands that you use and the amount of space actually reclaimed can vary Copyright IBM Corp 2013 All rights reserved 31 5 1 Space reclamation architecture After a host writes to a thin provisioned volume physical capacity is allocated to the host file system Unfortunately if the host deletes the file only the host file system frees up that space The physical capacity of the storage system remains unchanged In other words the storage system does not free up the capacity from the deleted host file This is commonly referred to as dead space Obviously this is not the most effective method for handling back end block level storage Ideall
16. Copyright IBM Corp 2013 All rights reserved 19 3 1 Performance There are no performance related considerations associated with XIV system thin provisioning This is because the XIV architecture provides a certain performance level that has to do with the data distribution the algorithms that handle the I O the performance capabilities of the XIV hardware and the nature of the I O characteristics to name a few All of the logical data constructs like a regular pool a thin pool or a LUN logical unit number or volume are virtualized logical entities that do not have any affect on performance 3 2 Application considerations 20 The most important enterprise applications are not typically the first choice for thin provisioning Here are examples of applications or parts of applications that might make good candidates for thin provisioning gt Test and development environments Unpredictable data size Dynamic use gt Crisis projects Often over request space due to no adequate planning time Backup application storage pool space The efficiency of thin provisioning is dependent on the behavior of your applications in general especially in the way that they allocate space for their data Carefully select applications whose characteristics can actually benefit from thin provisioning The application that performs this function is typically a file system or a database in cases where a file system is not used Ide
17. Example 5 1 Discovering and checking new disks on your host vxdisk f scandisks vxdisk list DEVICE TYPE DISK GROUP STATUS disk_0 auto ZFS ZFS disk 1 auto ZFS ZFS disk 2 auto ZFS ZFS disk_3 auto ZFS ZFS xiv0 251a auto none online invalid xiv0 251b auto none online invalid 4 After you discover the new disks on the host you might need to format the disks For more information see your OS specific Symantec Storage Foundation documentation In this example the disks must be formatted Run the vxdiskadm command as shown in Chapter 5 Space reclamation with XIV 41 42 Example 5 2 Select option 1 and then follow the instructions accepting all defaults except for these questions a Encapsulate this device answer no b Instead of encapsulating initialize answer yes Example 5 2 Configuring disks for VxVM vxdiskadm Volume Manager Support Operations Menu VolumeManager Disk 1 Add or initialize one or more disks 2 Encapsulate one or more disks 3 Remove a disk 4 Remove a disk for replacement 5 Replace a failed or removed disk 6 Mirror volumes on a disk 7 Move volumes from a disk 8 Enable access to import a disk group 9 Remove access to deport a disk group 10 Enable online a disk device 11 Disable offline a disk device 12 Mark a disk as a spare for a disk group 13 Turn off the spare flag on a disk 14 Unrelocate subdisks back to a disk 15 Exclude a disk from hot re
18. IBM XIV Storage System Thin Provisioning and Space Reclamation Thin provisioning explored am conte Red naper International Technical Support Organization IBM XIV Storage System Thin Provisioning and Space Reclamation June 2013 REDP 5001 00 Note Before using this information and the product it supports read the information in Notices on page v First Edition June 2013 This edition applies to Version 3 2 of the IBM XIV Storage System with Storage Software Version 11 2 Copyright International Business Machines Corporation 2013 All rights reserved Note to U S Government Users Restricted Rights Use duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp Contents Notices oio Male eee eine ei Ss ie ees ee V rademarkS a ste se NAA Ec o sad eet LEA IN eL Mar em tei DA o M rz vi Preface n onc ee en e Se ee aed de epe er Pc a PERDU E DA vii Authors iu sod eb ur So ee gt d epe OE Ip dre terre niei a vii Now you can become a published author too liliis viii Comments welcome ssssssseeeeee remm viii Stay connected to IBM Redbooks 000 e eee eee tenes ix Chapter 1 Thin provisioning overview 0 0000 c eee eee 1 1 1 Thin provisioning introduction 0 eee 2 1 2 The business case for thin provisioning llle 3 1 2 1 IT without thin provisioning costly and complex 00 0c eee eee ee 3 1 2 2 Advantages of thin p
19. NSE This information contains sample application programs in source language which illustrate programming techniques on various operating platforms You may copy modify and distribute these sample programs in any form without payment to IBM for the purposes of developing using marketing or distributing application programs conforming to the application programming interface for the operating platform for which the sample programs are written These examples have not been thoroughly tested under all conditions IBM therefore cannot guarantee or imply reliability serviceability or function of these programs Copyright IBM Corp 2013 All rights reserved v Trademarks IBM the IBM logo and ibm com are trademarks or registered trademarks of International Business Machines Corporation in the United States other countries or both These and other IBM trademarked terms are marked on their first occurrence in this information with the appropriate symbol or indicating US registered or common law trademarks owned by IBM at the time this information was published Such trademarks may also be registered or common law trademarks in other countries A current list of IBM trademarks is available on the Web at http www ibm com legal copytrade shtml The following terms are trademarks of the International Business Machines Corporation in the United States other countries or both AIX IBM FlashSystem 390 DB2 Redbooks S
20. ally the space allocation of the applications should have the following characteristics to benefit from thin provisioning The application tends to localize its data in contiguous regions rather than scatter the data across the assigned volume The application tends to reuse previously used space before using new space that was never used before When the file system or database deletes data the space used by this deleted data is not automatically released The application storage needs tend to increase predictably over time The application file system or database might manage data in such a way that it ends up fully allocating the volume even when the stored data at any given time is actually much less than the full volume capacity In general the use of a Logical Volume Manager LVM is not expected to have a negative impact on thin provisioning If the LVM allows a logical volume to be subdivided into partitions Ideally create the partition boundaries aligned with an extent boundary of the logical volume to improve the likelinood that the extent remains unallocated This might not be easy to determine in practice If a file system is used this file system is expected to be the determining factor regarding the interaction with thin provisioning Databases can usually operate with or without a file system Without a file system the database behavior is expected to be the determining factor IBM XIV Thin Provisioning and Spa
21. ata still resides on the storage system A few file systems support an API to a storage system notifying the storage of a space that is freed These file systems enjoy an immediate space reclamation VxFS Microsoft Windows 2012 and Windows 8 are the only file systems with APIs that have been tested and certified with the XIV system Refer to Chapter 5 Space reclamation with XIV on page 31 The XIV system also has the concept of zero detection reclamation During the XIV Storage System scrubbing process when a partition is found that contains data composed of all zeros the XIV system logically maps that data to metadata containing zeros and reclaims that partition as free available hard space In other words in XIV storage zeros are free and do not take up real data storage capacity To use the XIV storage system s zero detection reclamation zeros have to be written to host file system or raw volume areas before those areas are deleted The XIV scrubbing process runs all the time and reclaiming this zero space is automatic These are some examples of how to zero space gt On Windows SDelete z On UNIX or Linux dd if dev zero of file name bs 2048 On Oracle ASM ASRU utility Chapter 3 Thin provisioning considerations 21 3 5 File system considerations Some operating system file systems receive good space saving benefits from thin provisioning and others receive little benefit For a file system to be thin pro
22. capacity for each user as thin provisioned volumes though in the back end storage the real capacity per user only amounts to 6 GB If we assume 100 users this means that the virtual capacity is 1 TB but only 600 GB of real capacity is available in the storage subsystem This is a valid approach only because the administrator knows from previous observations that not all users will request the whole amount of physical capacity at the same time Some will only request 4 GB or less some might request the whole 10 GB But the assumption remains that on average they all request no more than 6 GB of real capacity It remains the responsibility of the storage administrator to monitor the allocation of real capacity to avoid any out of space condition IBM XIV Thin Provisioning and Space Reclamation Thin provisioning planning and usage This chapter contains information about how you can determine an appropriate XIV system configuration with thin provisioning in a given environment and uses an illustrated example to review implementation best practices Copyright IBM Corp 2013 All rights reserved 25 4 1 Planning implementation and helpful processes 26 To determine an appropriate XIV system configuration with thin provisioning in a given environment carefully gather the following required data The order is not relevant at this point but gather the information contained in these steps before you implement XIV thin provisioning
23. ce Reclamation regarding the interaction with thin provisioning For instance if the database has the characteristic of initializing all of its configured table spaces any associated volumes end up fully allocated making thin provisioning useless in this case Note It is beyond the scope of this Redpaper publication to identify specific software or applications with regards to their compatibility with the XIV thin provisioning feature 3 3 XIV Storage System Generation 2 and Gen3 differences XIV Storage System Gen software contains enhancements that benefit thin provisioning gt Offsetting the beginning of where data is written within an XIV volume Using a prime number algorithm to ensure that no repeating data patterns can have a negative impact on data distribution within the XIV volume In environments where there are many volumes significantly smaller than any multiple of 17 GB the space over the 17 GB multiple is wasted That is given a 1 GB volume or an 18 GB volume each wastes approximately 16 GB Defining pools with many such volumes as thin provisioned pools significantly reduces the amount of wasted capacity 3 4 Data reclamation Data reclamation is a major factor in enjoying the benefits of thin provisioning Consider applications that write huge amounts of data and then delete the data Normally this space is not available for reuse because the file system only removes the pointers to the data but all the actual d
24. d pattern list all list q xivO 251a xiv0 251b Here are the disks selected Output format Device Name xiv0 251a xivO 251b Continue operation y n q default y You can choose to add these disks to an existing disk group a new disk group or you can leave these disks available for use by future add or replacement operations To create a new disk group select a disk group name that does not yet exist To leave the disks available for future use specify a disk group name of none Which disk group lt group gt none list q default none XIV DG Create a new group named XIV DG y n q default y Create the disk group as a CDS disk group y n q default y Use default disk names for these disks y n q default y Add disks as spare disks for XIV DG y n q default n Exclude disks from hot relocation use y n q default n Add site tag to disks y n q default n A new disk group will be created named XIV DG and the selected disks will be added to the disk group with default disk names xiv0 251a xivO 251b Continue with operation y n q default y The following disk devices have a valid VTOC but do not appear to have been initialized for the Volume Manager If there is data on the disks that should NOT be destroyed you should encapsulate the existing disk partitions as volumes instead of adding the disks as new disks Output format Device Name xiv0 251a xivO 251b Encapsulat
25. d 20 357 of 131 418 GB 15 ta Ga Soft 20 357 of 131 418 GB 15 E Figure 2 8 Regular provisioning When the system soft size is greater than the system hard size the XIV system by definition is over provisioned In Figure 2 4 notice that the hard system limit is 159 726 GB and the soft system limit is set at 326 008 GB EE 2005 co 02 s Figure 2 4 System level over provisioning It is possible and even common for the system hard and soft capacity settings to be equal and still use XIV thin provisioning This is called basic mode thin provisioning Indeed when you first experiment with XIV thin provisioning this is the usual case You realize XIV thin provisioning benefits but they will not be as significant as when the system soft capacity is extended beyond the hard capacity and storage capacity can be offered to host systems that exceeds the amount of purchased hard capacity This is called advanced mode thin provisioning or system over provisioning Clients who use regular provisioning usually begin to think about over provisioning when the system soft capacity approaches the system hard capacity and space becomes a premium In general this is when the system hard capacity utilization is only around 50 Before the XIV system when you were no longer able to allocate more storage it was time to buy more storage The XIV system so clearly shows the difference between soft system and hard system ca
26. databases and is space freed when data is deleted or rows removed from tables 22 IBM XIV Thin Provisioning and Space Reclamation Different systems offer the ability to reclaim space gt IBM DB2 version 9 7 introduced a space reclamation feature that can reduce the physical space used by database files when rows are deleted gt Oracle database with Automatic Storage Management ASM offers a possibility to reclaim unused space in the database by using the administrative asru command which is a manual three phase script Chapter 3 Thin provisioning considerations 23 3 6 Thin provisioning for user data 24 As a simple example consider user data in a business environment Such data is similar for most users and might consist of local mail replica cached data from web browsers and other application data commonly found in a business environment In addition most users have similar capacity requirements for this type of data However some users can also have specific applications with different capacity requirements For example users who are working most of the time with documents spreadsheets and presentations require less capacity than those working with images other multimedia data or other binary and scientific data Assuming that no user is requesting more than 10 GB of data and that the average of effectively used data is less than 6 GB per user the storage administrator might decide to allocate 10 GB of virtual
27. defaul t vxdisk with a value reclaim off 5 2 3 Space reclamation with VMware VMware began supporting SCSI UNMAP commands when it introduced the VMware vSphere 5 0 storage APIs for Array Integration VAAI primitives However VMware discovered issues which affected their Storage vMotion and VM Snapshot consolidation that led them to alter their SCSI UNMAP support for its newest release vSphere 5 1 Specifically vSphere 5 1 does not provide proactive or automatic space reclamation for SCSI UNMAP commands Manual user intervention or scripts must be implemented to realize the SCSI UNMAP benefits preferably outside of peak business hours However because it is enabled by default in V11 2 running VMware 5 0 means that space reclamation is enabled automatically Chapter 5 Space reclamation with XIV 45 46 IBM XIV Thin Provisioning and Space Reclamation Related publications The publications listed in this section are considered particularly suitable for providing more detailed information about the topics covered in this paper IBM Redbooks The following IBM Redbooks publications provide additional information about the topic in this document Note that some publications referenced in this list might be available in softcopy only gt gt gt gt gt IBM XIV Storage System Copy Services and Migration SG24 7759 IBM XIV Storage System Host Attachment and Interoperability SG24 7904 Solid State Drive Caching in th
28. dependent on conditions in the storage system involved The following operating systems support the UNMAP command with XIV storage gt With XIV Storage System V11 2 or later XIV Storage System Gen3 provides support for the SCSI UNMAP function natively available with Microsoft Windows Server 2012 Note that from an OS perspective Microsoft Windows uses file TRIM or FILE_LEVEL_TRIM code to trigger storage space reclamation using either TRIM or SCSI UNMAP requests depending on the target device types Consequently for Microsoft Windows solutions file TRIM and space reclamation are often used interchangeably due to their obvious relationship VMware began supporting SCSI UNMAP commands when it introduced the VMware vSphere 5 0 storage APIs for Array Integration VAAI primitives However VMware discovered issues that affected their Storage vMotion and VM Snapshot consolidation which led them to alter their SCSI UNMAP support for their newest release vSphere 5 1 Specifically vSphere 5 1 does not provide proactive or automatic space reclamation for IBM XIV Thin Provisioning and Space Reclamation SCSI UNMAP commands Manual user intervention or scripts must be implemented to realize the SCSI UNMAP benefits preferably outside of peak business hours 5 1 2 WRITE SAME command The WRITE SAME command with the UNMAP bit 1 can be used to reclaim unused capacity This command has the following characteristics gt It writes zeros to
29. e IBM XIV Storage System REDP 4842 Using the IBM XIV Storage System in OpenStack Cloud Environments REDP 4971 XIV Storage System in a VMware Environment REDP 4965 You can search for view download or order these documents and other Redbooks Redpapers web docs drafts and additional materials at the following website http ibm com redbooks Other publications These publications are also relevant as further information sources gt gt gt IBM XIV Remote Support Proxy Installation and User s Guide GA32 0795 IBM XIV Storage System Application Programming Interface GC27 3916 IBM XIV Storage System Planning Guide GC27 3913 IBM XIV Storage System Product Overview GC27 3912 IBM XIV Storage System Commands Reference GC27 3914 IBM XIV Storage System Management Tools version 4 0 User Guide SC27 4230 IBM XIV Storage System XCLI Utility User Manual GC27 3915 The iSCSI User Guide found at http download microsoft com download a e 9 ae91deal 66d9 417c ade4 92d824b87 1 af uguide doc Copyright IBM Corp 2013 All rights reserved 47 Online resources These websites are also relevant as further information sources gt IBM XIV Storage System Information Center http publib boulder ibm com infocenter ibmxiv r2 index jsp gt IBM XIV Storage website http www ibm com systems storage disk xiv index htm gt System Storage Interoperability Center SSIC http www ibm com systems support storage config
30. e are real cost savings benefits associated with thin provisioning These cost savings include acquisition costs power and cooling costs and administration costs among others Because XIV thin provisioning is a logical entity there is great flexibility involved in using thin provisioning When the application is running with no performance or downtime consideration you can perform the following tasks Change an XIV storage pool from regular to thin and back again Change the pool capacity Move the actual LUN between different storage pools Thin provisioning is not for every storage allocation situation Initially use this provisioning capability carefully because it provides the appearance of more data storage capacity than is actually physically allocated Thin provisioning requires caution and close monitoring XIV provides sophisticated storage pool monitoring and alerting mechanisms to ensure that a storage pool never runs out of room to store data Test these mechanisms to ensure that the email and text alerting functions work properly especially when using thin provisioning There are certain considerations outside of XIV thin provisioning capabilities that can help set expectations for the degree to which thin provisioning will effectively provide more efficient data storage capacity usage These considerations include things like file system types and the way an application reuses data within the file system I
31. e these devices Y N S elect q default Y N xiv0 251a xivO 251b Instead of encapsulating initialize Y N S elect q default N Y Do you want to use the default layout for all disks being initialized y n q default y Initializing device xivO 251a Chapter 5 Space reclamation with XIV 43 44 Initializing device xiv0 251b VxVM NOTICE V 5 2 120 Creating a new disk group named XIV_DG containing the disk device xivO 251a with the name XIV DGO1 VxVM NOTICE V 5 2 88 Adding disk device xiv0 251b to disk group XIV DG with disk name XIV DG02 Add or initialize other disks y n q default n Tip If the vxdiskadm initialization function warns that the disk is offline you might need to initialize it using the default OS specific utility For example use the format command in Solaris 5 Check the results by using the vxdisk list command as shown in Example 5 3 Example 5 3 Showing the results of putting XI V LUNs under VxVM control vxdisk list DEVICE TYPE DISK GROUP STATUS disk 0 auto ZFS ZFS disk 1 auto ZFS ZFS disk 2 auto ZFS ZFS disk 3 auto ZFS ZFS xiv0 251a auto cdsdisk XIV_DGO1 XIV_DG online thinrclm xiv0 251b auto cdsdisk XIV DGO2 XIV DG online thinrclm The XIV LUNs that were added are now available for volume creation and data storage The status thinrclm means that the volumes from the XIV system are thin provisioned and the XIV storage has the Veritas thin reclamation
32. eclamation considerations llli 33 5 2 Space reclamation and operating systems liii illie rsen 34 5 2 1 Windows 2012 space reclamation 0 00 eee eese 34 5 2 2 Veritas space reclamation 0 eee eee 40 5 2 3 Space reclamation with VMware 00 00 e eee ee 45 Related publications 2 0 teas 47 IBM RedboOkS c ee ee a ASE Se ai er Dresses RR A feque 47 Other publications t oet sucus TEDA pea dd ae eat ate es open RAD ae TE 47 Online resources sss cst senes x e vae bio ee esie sa Ene d aka a 48 Copyright IBM Corp 2013 All rights reserved iii iv Help trom IBM sre mas sp drag alae DE wade Peeled be bold aw a bes Da Se IBM XIV Thin Provisioning and Space Reclamation Notices This information was developed for products and services offered in the U S A IBM may not offer the products services or features discussed in this document in other countries Consult your local IBM representative for information on the products and services currently available in your area Any reference to an IBM product program or service is not intended to state or imply that only that IBM product program or service may be used Any functionally equivalent product program or service that does not infringe any IBM intellectual property right may be used instead However it is the user s responsibility to evaluate and verify the operation of any non IBM product program or service
33. enabled by default in Windows 2012 follow these steps 1 Start Registry Editor 2 Locate the following registry subkey HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Control FileSystem 3 Double click DisableDeleteNotification 4 In the Value data box enter a value of 1 and click OK Realize that if you configure this setting this disables the file delete notification for all LUNs that are assigned to the host If file delete notification is disabled you can still use the Defragment and Optimize Drives tool to perform space reclamation on demand or on a scheduled basis Pool thresholds notification You can use the XIV Storage Management GUI to configure pool usage thresholds to trigger color coded visual alerts at various severity levels These alerts are system based across all pools and are viewable in the XIV Storage Management GUI by all users configured with the particular system System events are also produced based on specified values The default pool usage threshold values are for warning 80 minor 90 and major 95 as shown in Figure 5 1 You can set rules to receive email alerts for these events Pool Alert Thresholds Volumes Usage O Informational Snapshots Usage Warning 80 9 v Minor M 90 1 v Major M 95 Critical Restore Factory Defaults Ea Es Figure 5 1 Pool thresholds in XIV GUI Alert thresholds are no
34. ge capacity or change application or user behavior Thin provisioning is implemented on the storage level and is completely transparent to the host using the volume There are a couple of good similes to better understand thin provisioning The first is that thin provisioning is like virtual memory in an operating system getting something for nothing The other is that thin provisioning is like when airlines overbook seats on a flight which is generally a good thing but can lead to problems if not managed properly IBM XIV Storage System Thin Provisioning and Space Reclamation 1 2 The business case for thin provisioning There are several business situations that can justify storage thin provisioning This section reviews some of those situations and shows why XIV is usually a good fit 1 2 1 IT without thin provisioning costly and complex As an IT manager or storage administrator you must manage the cost of storage You are likely faced with burgeoning organizational demands for storage capacity yet expected to curb storage expenses In this section we examine how traditional approaches to storage allocation and thin provisioning actually inflate costs Capacity gone to waste One of the disturbing facts about storage costs is that 70 or more of the storage capacity in enterprise settings goes unused Storage space is allocated to an application but the application uses only a portion of it This waste is caused by several factors
35. ges of thin provisioning It can be easy for you to administer and manage storage pools because pools are a purely logical entity You can always resize a storage pool move storage capacity between storage pools or move volumes between storage pools Pools are not associated with any physical entity such as a disk drive or module In fact all storage pools are distributed equally in the XIV system among all hardware components The ability to reclaim logically unused capacity The XIV system also has a sophisticated mechanism to reclaim unused areas of the volume even after they have been defined as used The effect of this feature is that you can decrease used capacity if used data is logically erased by writing all zeros You can use this capability to reclaim space in several scenarios When migrating volumes from existing storage equipment to XIV storage parts of the volume that are all zeros are marked unused and will not consume physical space When an application writes a long sequence of zeros the relevant part is marked unused even if previous information was not zero As a background process the XIV storage system scans volumes and searches for long areas that are all zeros marking these areas unused This reclaiming process provides huge potential savings especially when you migrate storage from existing systems The operational cost reduction power cooling and floor space per TB associated with the XIV system is
36. hin provisioning involves the risk that the actual storage usage will grow unexpectedly and rapidly and will reach the actual physical data storage capacity of the storage system with still further unsatisfied demand You need to identify and correct any situations where space utilization is approaching the hard data storage capacity of the system This requires some administrative effort on a regular basis to monitor the system space utilization gt If the space utilization actually reaches the hard data storage capacity of the storage system migration off the storage system to another storage system with free space is required involving significant administrative effort The online migration capabilities of XIV make this task much easier gt If the space utilization actually reaches the hard data storage capacity of the storage system any running application will stop in a way that cannot be predicted At a minimum the application will stop and application downtime will be experienced unexpectedly This is never a pleasant experience Summary Thin provisioning is an important technological improvement that can solve many storage problems The ability to separate the logical view of the system from the actual capacity provisioned and procured provides you a significant cost savings and enhances ease of management However traditional thin provisioning comes with several management challenges Thin provisioned systems need to be
37. ial hard system size It is for this reason that defining the soft system size is not within the scope of the storage administrator role gt If you want to increase the soft system size beyond the maximum hard system size for a particular XIV system model there is a procedure that IBM performs that can accomplish this task This change has no impact on the XIV operation Contact your IBM Technical Advisor for further details 2 1 3 System level thin provisioning The XIV system has the concept of hard capacity and soft capacity Hard capacity or hard system size has to do with the maximum physical data storage capacity of the XIV system Soft capacity or virtual capacity is the maximum limit of LUN capacity that you can configure on the XIV system Chapter 2 Thin provisioning in XIV 15 16 The XIV architecture enables you to define a global system capacity in terms of both a hard system size and a soft system size When over provisioning is not activated at the system level these two sizes are equal to the system s physical capacity The system capacity graphics from a regularly provisioned system are shown in Figure 2 3 Notice that the total system hard and soft sizes are both 131 418 GB The hard size and the soft size can be toggled by selecting the up and down arrows on the right side of either graphic Because these two values are equal this XIV system has not activated thin provisioning at the system level Gom Har
38. iles are moved the reclaimed space 34 GB shows up as capacity allocated to the Snapshot Therefore the overall allocated capacity in the Pool has actually increased as shown in Figure 5 11 Usage Snapshots GB 120 GB Used Volumes of 309 GB Hard309 GB Hard Used 34 GB 22 hua M L 1 2 TB Volumes allocated 2 TB Soft Snapshots reserved 154 GB Figure 5 11 Snapshot capacity allocation Tip Be careful to allocate sufficient hard capacity in the Storage Pool and Snapshot area There is a delay between the actual data updates and the space reclamation which can require additional physical hard capacity in the pool If the Storage Pool becomes full snapshots might be deleted 5 2 2 Veritas space reclamation 40 The Symantec Storage Foundation is available as a unified method of volume management at the OS level It was formerly known as the Veritas Volume Manager VxVM and Veritas Dynamic Multipathing DMP At the time of this writing the XIV system supports the use of VXVM and DMP with the following operating systems HP UX IBM AIXO Red Hat Enterprise Linux SUSE Linux Linux on Power Solaris vvvvvy IBM XIV Thin Provisioning and Space Reclamation Depending on the OS version and hardware only specific versions and releases of Veritas Volume Manager are supported when connected to the XIV system In general IBM software supports VxVM versions 5 0 and 5 1 For most of the OS and VxVM versions IBM suppor
39. ind us on Facebook http www facebook com IBMRedbooks gt Follow us on Twitter http twitter com ibmredbooks gt Look for us on LinkedIn http www linkedin com groups home amp gid 2130806 Explore new Redbooks publications residencies and workshops with the IBM Redbooks weekly newsletter https www redbooks ibm com Redbooks nsf subscribe 0penForm gt Stay current on recent Redbooks publications with RSS Feeds http www redbooks ibm com rss html Preface ix x IBM XIV Thin Provisioning and Space Reclamation Thin provisioning overview For most businesses managing a storage environment is an endless balancing act of providing enterprise class functionality and services but still controlling costs One area that is a considerable component in capital and operational costs is unused storage space that is allocated to applications but is not being used Thin provisioning is the practice of allocating storage to applications on a just in time and as needed basis by defining a logical capacity that is larger than the physical capacity This common practice is a means to reducing or postponing storage costs Tip Thin provisioning is a no charge feature of IBM XIV Storage System software XIV storage has a native virtual architecture XIV thin provisioning is nothing more than a different way of displaying the XIV storage pools to the XIV management GUI The underlying data structures do not change between XIV regula
40. ion You can optimize your drives to help your computer run more efficiently or analyze them to find out if they need to be optimized Only drives on or connected to your computer are shown Status Drive Media type Last run Current status Es C Hard disk drive OK 0 fragmented 1 oned drive OK 10 ce OK 100 space efficiency OK 0 fragmented Never run cs XIV Volume 2 Fi ca System Reserved Thin provisioned drive 3 28 2013 3 00 AM Hard disk drive Never run Optimize Scheduled optimization On Change settings Drives are being optimized automatically Frequency Daily Close Figure 5 2 Optimize Drives menu In this scenario files are created on the drives and use 67 GB of physical space as shown in Figure 5 3 az XIV Volume 1 D Properties Shadow Copies Previous Versions Quota Customize Shadow Copies Previous Versions Quota Customize General Tools Hardware Sharing Security General Tools Hardware Sharing Security c XIV Volume 1 Type Local Disk Type Local Disk File system NTFS File system NTFS Bl Used space BB Free space 67 323 494 400 bytes 625GB 534 826 450 944 bytes 498 GB Capacity 602 149 945 344 bytes 560 GB Drive D Allow files on this drive to have contents indexed in addition to file properties 67 323 363 328 bytes 525 GB 534 826 582 016 bytes
41. ion approaching hard space depletion you cannot add more modules The next section explores considerations for hard space depletion 2 1 4 Out of space considerations Using thin provisioning creates the inherent danger of exhausting the available physical capacity If the soft system size exceeds the hard system size the potential exists for applications to fully deplete the available physical capacity It is difficult to consider a situation where this condition can be tolerated in a production environment Thin provisioning requires planning and monitoring It is important to determine the proper over provisioning ratio for a given application environment and a realistic data growth average over time Use the XIV storage pool threshold alerting mechanisms provided to receive warnings ahead of time For this purpose you need to set the thresholds according to your individual needs which are driven by the workload and application characteristics and importance The thin provisioning implementation in the XIV system manages space allocation within each storage pool so that hard capacity depletion in one storage pool never affects the hard capacity available to another storage pool Snapshot deletion As mentioned previously snapshots in regular storage pools can be automatically deleted by the system to provide space for newer snapshots For thinly provisioned pools snapshots can be deleted to free more physical space for volumes Volume
42. ject with a 70 non utilization rate and a budgeted capital expense of 1 000 000 you can implement the project using a thin provisioned system for only 300 000 gt Environmental factors The unused capacity consumes electricity and generates heat adding to power and cooling expenses As with capital expenses a storage project with a 70 non utilization rate costs only 30 of the power and cooling if implemented with thin provisioning Chapter 1 Thin provisioning overview 3 gt Floor space The same analysis applies to savings in floor space which is another expensive resource involving the cost of building raised floors uninterrupted power supply systems cooling systems and so on that is often in short supply gt Declining storage costs over time Without thin provisioning you must purchase storage at the time of allocation sometimes years before it is used This scenario involves doubling your costs not only are power cooling and floor space wasted during the time of the storage not being used but your organization is unable to take advantage of yearly declines in the cost of storage Also the power and space efficiency of storage systems improves over time these advantages go untapped when you buy storage up front 1 2 2 Advantages of thin provisioning in the XIV system 4 XIV Storage System software provides many capabilities to improve data storage efficiency including usage monitoring storage pools reclai
43. location use 16 Make a disk available for hot relocation use 17 Prevent multipathing Suppress devices from VxVM s view 18 Allow multipathing Unsuppress devices from VxVM s view 19 List currently suppressed non multipathed devices 20 Change the disk naming scheme 21 Get the newly connected zoned disks in VxVM view 22 Change Display the default disk layouts list List disk information Display help about menu Display help about the menuing system q Exit from menus Select an operation to perform 1 Add or initialize disks Menu VolumeManager Disk AddDi sks Use this operation to add one or more disks to a disk group You can add the selected disks to an existing disk group or to a new disk group that will be created as a part of the operation The selected disks may also be added to a disk group as spares Or they may be added as nohotuses to be excluded from hot relocation use The selected disks may also be initialized without adding them to a disk group leaving the disks available for use as replacement disks More than one disk or pattern may be entered at the prompt Here are some disk selection examples IBM XIV Thin Provisioning and Space Reclamation all all disks C3 c4t2 all disks on both controller 3 and controller 4 target 2 c3t4d2 a single disk in the c t d naming scheme xyz 0 a single disk in the enclosure based naming scheme XyZ all disks on the enclosure whose name is xyz Select disk devices to ad
44. locking If you still require more hard capacity after all the snapshots in a thinly provisioned storage pool have been deleted all the volumes in the storage pool are locked preventing any additional use of hard capacity There are two possible behaviors for a locked volume gt Read only the default behavior gt No lO at all In either case your applications stop in a way that is not predictable Important Volume locking prevents writes to all volumes in the storage pool Avoid this condition It is worth considering the differences between a regular pool running out of space and a thin pool running out of space The size of a regular pool is determined by the application owner If that application uses all of the space the application normally knows how to handle the out of space condition If the application has issues it is certainly not the storage administrator s fault because the application owner did not request adequate space Now consider the case where the application owner has asked for a certain amount of space and by all appearances that amount of space was delivered but in fact less real hard data Chapter 2 Thin provisioning in XIV 17 18 storage capacity was delivered This is thin provisioning In this case the application can run out of space unexpectedly Although it is usually incumbent upon the application to know how to handle an out of space condition it is not reasonable to expect an application to k
45. loped by the IBM International Technical Support Organization Experts from IBM Customers and Partners from around the world create timely technical information based on realistic scenarios Specific recommendations are provided to help you implement IT solutions more effectively in your environment For more information ibm com redbooks
46. lume areas that were written by hosts The actual volume size is not controlled directly by the user and depends only on the application behavior Volume size starts from zero at volume creation or formatting and can reach the logical volume size when the entire volume has been written Resizing of the volume affects the logical volume size but does not affect the actual volume size The actual volume size reflects the physical space used in the volume as a result of host writes It is discretely and dynamically provisioned by the system not the storage administrator The discrete additions to actual volume size can be measured in two ways by considering the allocated space or the consumed space The allocated space reflects the physical space used by the volume in 17 GB increments The consumed space reflects the physical space used by the volume in1 MB partitions In both cases the upper limit of this provisioning is determined by the logical size assigned to the volume gt Capacity is allocated to volumes by the system in increments of 17 GB due to the underlying logical and physical architecture there is no smaller degree of granularity than 17 GB gt Application write access patterns determine the rate at which the allocated hard volume capacity is used and therefore the rate at which the system allocates additional increments of 17 GB up to the limit defined by the logical volume size As a result the storage administrator has no di
47. ming capacity and snapshots Capacity usage monitoring The XIV storage system has robust capabilities to monitor pool storage consumption constantly and enables the storage administrator to configure the system to send notifications when space utilization exceeds a user defined threshold These notifications can be sent to various destinations as simple network management protocol SNMP traps emails or text messages The severity and destination of the notification depends on the actual consumption threshold passed The whole idea of thin provisioning monitoring is to never run out of physical capacity You can configure the XIV system so that if a given event notification is not handled within a certain time period another event notification is sent to the same addressees or to a broader distribution list like a manager Thin provisioning limited to specific applications Another important feature of the XIV storage system is that you can manage thin provisioning per storage pool The concept of a storage pool is unique to the XIV system a storage pool is a logical entity defined in the system which contains a group of volumes and their snapshots Each storage pool limits the amount of space that the volumes and snapshots belonging to the pool can consume Within a production XIV environment it is common to have a mix of fully provisioned storage pools and thin provisioned storage pools You can define a thin provisioning policy per
48. n the form of individual modules and associated disks or groups of modules There are situations such as rebuilds and redistributions that can temporarily reduce the system s hard limit Soft system size The soft system size is the total global and logical space available for all storage pools in the system When the soft system size exceeds the hard system size it is possible to logically provision more space than is physically available realizing the benefits of thin provisioning of storage pools and volumes at the system level The soft system size limits the soft size of all volumes in the system and has the following attributes gt Soft size is not related to any direct system attribute and you can define it to be larger than the hard system size if thin provisioning is implemented The storage administrator cannot set the soft system size gt ideally in a partially populated XIV configuration using thin provisioning when the limits of the XIV system s soft size is being challenged by the growth of the hard data storage requirements your can purchase additional modules to alleviate the danger of running out of hard capacity Important Upgrading an XIV system beyond the full 15 modules in a single frame is not supported at the time of this writing gt The soft system size is a purely logical limit however and you must exercise care when the soft system size is set to a value greater than the maximum potent
49. napshots being deleted if additional pool space is needed gt UNMAP is supported for volumes that use synchronous mirroring as long as all of the XIV systems are using V11 2 or later code Restriction UNMAP is not supported for volumes that use asynchronous mirroring Chapter 5 Space reclamation with XIV 33 5 2 Space reclamation and operating systems Operating systems with the following characteristics are considered compatible with thin provisioning gt Localized data placement unused capacity is not pre initialized gt Reuse of freed space write to previously used and deleted space before writing to never used space When file system space is deleted that information is communicated to the storage system so that reclamation can take place This is implemented with the UNMAP or WRITE SAME commands described in 5 1 Space reclamation architecture on page 32 The operating systems listed in Table 5 1 currently support space reclamation Table 5 1 Operating systems that support space reclamation Red Hat Linux Usually uses UNMAP depending on the file system in use VMware vSphere 5 x Using UNMAP currently disabled by default Restriction At the time of this writing the IBM XIV Storage System software does not support Red Hat Linux and VMware vSphere 5 x space reclamation 5 2 1 Windows 2012 space reclamation 34 XIV Storage System V11 2 software supports the Windows 2012 UNMAP implementation Imp
50. ned environments coupled with the latest space reclamation enhancements Authors This paper was produced by a team of specialists from around the world working at the International Technical Support Organization ITSO San Jose Center Bertrand Dufrasne is an IBM Certified Consulting IT Specialist and Project Leader for IBM System Storage disk products at the ITSO San Jose Center He has worked at IBM in various IT areas He has authored many IBM Redbooks publications and has also developed and taught technical workshops Before joining the ITSO he worked for IBM Global Services as an Application Architect He holds a Master s degree in Electrical Engineering Christian Burns is an IBM Storage Solution Architect based in New Jersey As a member of the Storage Solutions Engineering team based in Littleton MA he works with clients business partners and IBM employees worldwide designing and implementing storage solutions that include a variety of IBM products and technologies Christian s areas of expertise include real time compression SAN Volume Controller SVC XIV and IBM FlashSystem Prior to joining IBM Christian was the Director of Sales Engineering at Storwize He brings over a decade of industry experience in the areas of sales engineering solution design and software development Christian holds a BA degree in Physics and Computer Science from Rutgers College Guenter Rebmann is a certified XIV Product Field Engineer
51. now what to do when it unexpectedly runs out of space when it thinks plenty of space remains It is for this reason that XIV thin provisioning offers a choice of read only or no I O It is also why the application might stop in a way that might be unpredictable This is an uncomfortable situation for a storage administrator Attention It is irresponsible for a storage administrator to allow a thin provisioned pool to run out of real capacity If an application is so important that the risk of running out of space in a thin provisioned storage pool configuration is too great that application is simply not a candidate for thin provisioning In the XIV system it is common to have a mix of regular and thin provisioning Because storage pools are independent thin provisioning volume locking on one storage pool never cascades into another storage pool It is still possible for the storage administrator to intervene to increase pool hard capacity or to redistribute hard capacity between pools IBM XIV Thin Provisioning and Space Reclamation Thin provisioning considerations When you implement thin provisioning there are variables that result in a range of the degree of success This chapter contains information about these variables which include gt gt gt Performance Application considerations IBM XIV Storage System Generation 2 and Gen3 differences Data reclamation File system considerations User data differences
52. ns View Tools Hep Add Pool 5 Volumes by Pools Configure Pool Threshold Export admin All Systems 5 gt v Storage Pools Pool 3 System Time 1 29 AM O Name Usage Snapshots GB Lock Behavior 2 1 TB Used Volumes 3 4 TB Hard e resene Read only TB Volumes allocated of Ge Ke mo T oos TT ey 163 TB 7 TB Snapshots reserved 206 GE amp Rename E Change Lock Behavior Add Volumes 2 Properties A XIV 7820784 Coos e D Co Field D Figure 4 2 Resize storage pool 4 The Resize Pool window opens Select Thin Pool as shown in Figure 4 3 Resize Pool Test O e Regular Pool rz Hard 20 013 GB XIV 7820784 bs e Thin Pool SysemAllocated o f 1 357 GB Soft 20 013 GB Pool Hard Size Pool Soft Size Snapshots Size Lock Behavior 103 Read only Cancel Figure 4 3 Select thin pool The hard pool size in an XIV system thin pool always needs to contain enough data storage capacity to handle the hard data At the current data growth rate of less than 1 IBM XIV Thin Provisioning and Space Reclamation adding 20 to the current hard data can provide well over 10 years of growth This calculation yields a thin pool hard size of 2529 GB 5 Make the soft pool size 50 larger than the hard size Add the volumes in the Test pool plus the snapshot space and the new soft space will be 3803 GB Also increase the new snapsho
53. o the logical volume when the associated applications execute writes as opposed to when the logical volume is initially allocated Because the total system capacity is designed as a globally available pool thinly provisioned resources share a buffer of free space which results in highly efficient aggregate capacity utilization without pockets of inaccessible unused space With the static inflexible relationship between logical and physical resources commonly imposed by traditional storage systems each application s capacity must be managed and allocated independently This situation often results in a large percentage of the total system capacity remaining unused because the capacity is confined within each volume at a highly granular level You can more effectively defer capacity acquisition and deployment until actual application and business needs demand additional space Acquisition costs operating costs cooling costs and administration costs all decrease with thin provisioning Thin provisioning defers the time in which the actual physical space has to be allocated At the same time from the application owner s perspective the current and future demands have already been met The XIV storage system has no performance penalty associated with using thin provisioning Thin provisioning has inherent risks that you need to understand and mitigate with proper storage administrative practices and procedures T
54. ogical volume size and the actual volume size The physical capacity allocated for the volume is not static but it increases as host writes fill the volume Logical volume size The logical volume size is the size of the logical volume that is observed by the host as defined upon volume creation or as a result of a resizing command The storage administrator specifies the volume size in the same manner regardless of whether the volume s storage pool is a thin pool or a regular pool The volume size is specified in one of two ways depending on units gt In terms of gigabytes The system allocates the soft volume size as the minimum number of discrete 17 GB increments needed to meet the requested volume size gt In terms of blocks The capacity is indicated as a discrete number of 512 byte blocks The system allocates the soft volume size consumed within the storage pool as the minimum number of discrete 17 GB increments needed to meet the requested size specified in 512 byte blocks However the size that is reported to hosts is equivalent to the precise number of blocks defined Incidentally the snapshot reserve capacity associated with each storage pool is a soft capacity limit and it is specified by the storage administrator although it effectively limits the hard capacity consumed collectively by snapshots as well IBM XIV Thin Provisioning and Space Reclamation Actual volume size The actual volume size is the total size of vo
55. ortant Upgrading to XIV Storage System V11 2 software by default enables UNMAP which will start being used immediately Considerations for using thin provisioning Considerations for using thin provisioning with Microsoft Windows 2012 are detailed in the Plan and Deploy Thin Provisioning article published by Microsoft at http technet microsoft com en us library jj674351 aspx The information in this section is taken directly from that article The following list summarizes those considerations gt There is predictable storage usage or a low volatile usage pattern on a storage volume The storage volume can tolerate a brief outage For example do not use thin provisioning if a mission critical cluster disk cannot tolerate any downtime or delays that are caused by thin provisioning That is there can be delays that are associated with temporary resource exhaustion or with space reclamation that occurs after large files are deleted IBM XIV Thin Provisioning and Space Reclamation There is an adequate storage monitoring process that detects when critical thresholds are crossed Well defined policies for monitoring and response are in place You understand the time requirement to acquire new storage If you do not understand the storage resource procurement process thin provisioned logical units LUNs might be exposed to the risk of permanent resource exhaustion If you do not want to use real time space reclamation which is
56. pacity that it almost forces you to consider thin provisioning because it is almost irresistible to ignore the promise of using some of that storage that is allocated but is not storing any data Also note that if the storage pools within the system are thinly provisioned but the soft system size does not exceed the hard system size the total system hard capacity cannot be filled until all storage pools are regularly provisioned As stated earlier if you want to increase the soft system size beyond the maximum hard system size for a particular XIV system model there is a procedure that IBM performs that can accomplish this task This change has no impact on the XIV system operation Contact your IBM Technical Advisor for further details IBM XIV Thin Provisioning and Space Reclamation System level thin provisioning by definition allocates more space than is physically available There is risk in this allocation decision You can mitigate this risk by planning and monitoring and by storage pool alerting mechanisms However the fact remains that a risk exists with thin provisioning that does not exist with regular pool provisioning The decision to assume this risk is much easier if the XIV system has a partially populated configuration With a partially populated XIV configuration as hard space is depleted it is simply a matter of purchasing more modules to add more hard capacity to the XIV system With a fully populated XIV system configurat
57. proach to thin provisioning This approach enables you to allocate capacity based on the total space actually used rather than just the space allocated The result is improved storage utilization rates leading to greatly reduced capital and operational costs Thin provisioning was a design requirement of the original XIV architecture XIV is a virtual storage system with data awareness Volumes storage pools and thin provisioning are all simply logical entities built around the data stored in the XIV system An XIV storage pool is either defined as being thin provisioned or fully provisioned During normal operations you can change an XIV storage pool from full provisioning to thin provisioning or as is commonly said from thin to full At any time you can move a simple volume from a thin pool to a full pool and back again You can implement these reconfigurations without any performance considerations An XIV storage pool is purely a logical entity just like the rules that define the behavior of thin and full storage pools XIV storage pools are not associated with any physical entity such as a disk drive a RAID array or an XIV module All storage pools and XIV volumes are distributed evenly among all hardware components in the XIV system Thin provisioning is a standard no cost feature of XIV Storage System software Thin provisioning can safely increase your storage utilization by up to 50 without requiring you to purchase more stora
58. project Eric Johnson Betty Porat Tedd Gregg Hans Paul Drumm Moriel Lechtmann and Shai Harony IBM Now you can become a published author too Here s an opportunity to spotlight your skills grow your career and become a published author all at the same time Join an ITSO residency project and help write a book in your area of expertise while honing your experience using leading edge technologies Your efforts will help to increase product acceptance and customer satisfaction as you expand your network of technical contacts and relationships Residencies run from two to six weeks in length and you can participate either in person or as a remote resident working from your home base Find out more about the residency program browse the residency index and apply online at http ibm com redbooks residencies html Comments welcome viii Your comments are important to us We want our papers to be as helpful as possible Send us your comments about this paper or other IBM Redbooks publications in one of the following ways gt Use the online Contact us review Redbooks form found at http ibm com redbooks Send your comments in an email to mailto redbooks us ibm com gt Mail your comments to IBM Corporation International Technical Support Organization Dept HYTD Mail Station P099 2455 South Road Poughkeepsie NY 12601 5400 IBM XIV Thin Provisioning and Space Reclamation Stay connected to IBM Redbooks gt F
59. r provisioning and thin provisioning Any XIV storage pool can be changed from regular provisioning to thin provisioning This reconfiguration is just a logical change yet there are important considerations and best practices associated with XIV Storage System thin provisioning that you need to understand Following an introduction to thin provisioning this chapter covers these topics The business case for thin provisioning gt How the XIV system implements thin provisioning XIV thin provisioning considerations XIV thin provisioning planning implementation and useful procedures including an implementation example Copyright IBM Corp 2013 All rights reserved 1 1 1 Thin provisioning introduction 2 Thin provisioning is becoming a widely accepted practice for data storage allocation because the cost and administrative benefits are easily realized Thin provisioning is the practice of providing virtual capacity to a logical volume logical unit number or LUN and passing that LUN to a host server The host sees the full capacity of the LUN when in fact the LUN is only backed with partial capacity or the capacity is dynamically allocated as data is written In this way thin provisioning provides significant improvements in data storage efficiency by overcoming the traditional problem of hosts only partially using the capacity of the LUNs assigned to them XIV The XIV system provides a highly flexible cost optimizing ap
60. rect control over the actual capacity allocated to the volume by the system at any given point in time gt During volume creation or when a volume is formatted there is zero physical capacity assigned to the volume As application writes accumulate to new areas of the volume the physical capacity allocated to the volume grows in increments of 17 GB and can ultimately reach the full logical volume size gt Increasing the logical volume size does not affect the actual volume size 2 1 2 Thinly provisioned storage pools Although the system effectively thinly provisions volumes automatically you can define storage pools when using the XIV Storage Management GUI as shown in Figure 2 1 on page 12 as either regular or thinly provisioned When you use the XIV Command Line Interface XCLI there is no specific parameter to indicate thin provisioning for a storage pool You indirectly and implicitly create a storage pool as thinly provisioned by specifying a pool soft size greater than its hard size With a regular pool the host apparent capacity is guaranteed to be equal to the physical capacity reserved for the pool The total physical capacity allocated to the constituent individual volumes and collective snapshots at any given time within a regular pool reflects the current usage by hosts because the capacity is dynamically used as required However the remaining deallocated space within the pool remains reserved for the pool and
61. rovisioning in the XIV system 0 00 eee ee eee 4 1 2 3 Advantages and disadvantages of thin provisioning 2 0 5 Chapter 2 Thin provisioning in XIV 0 00 00 ccs 9 2 1 Thin provisioning implementation in XIV auauua auaa a 10 2 1 1 Logical and actual volume sizes 10 2 1 2 Thinly provisioned storage pools ree 11 2 1 8 System level thin provisioning l i 15 2 1 4 Out of space considerations lille eee 17 Chapter 3 Thin provisioning considerations 000c cece else 19 3 1 Performance uus decedere m gen AR de er eoe Ede ay Ee E ak 20 3 2 Application considerations llle 20 3 3 XIV Storage System Generation 2 and Gen3 differences 00055 21 3 4 Data reclamation 0 00 cee tees 21 3 5 File system considerations 0 0 0 ce tees 22 3 6 Thin provisioning for user data 1 eee 24 Chapter 4 Thin provisioning planning and usage 0 0005 25 4 1 Planning implementation and helpful processes 00 eee eee eee 26 4 1 1 Thin provisioning implementation example lle eee 27 4 2 Thin provisioning conclusions slleseeeee II 29 Chapter 5 Space reclamation with XIV lliilsislslsl else 31 5 1 Space reclamation architecture lille 32 5 1 1 UNMAP command sseseeeeeee nn 32 5 1 2 WRITE SAME command sssselseses ren 33 5 1 3 XIV space r
62. scribed in Thinly provisioned storage pools on page 11 the storage administrator defines both the soft size and the hard size of thinly provisioned storage pools and allocate resources to volumes within a given storage pool without any limitations imposed by other storage pools You can dynamically change the designation of a storage pool as a regular pool or a thinly provisioned pool When you need to convert a regular pool to a thinly provisioned pool you must explicitly set the soft pool size parameter in addition to the hard pool size which remains unchanged unless updated When you need to convert a thinly provisioned pool to a regular pool the soft pool size is automatically reduced to match the current hard pool size If the combined allocation of soft capacity for existing volumes in the pool exceeds the hard pool size the storage pool cannot be converted This situation can be resolved if you selectively resize or delete individual volumes or move them to another storage pool to reduce the soft space used IBM XIV Thin Provisioning and Space Reclamation Hard system size The hard system size represents the physical disk capacity that is available within the XIV system This is the amount of data storage capacity that is purchased Obviously the system s hard capacity is the upper limit of the aggregate hard capacity of all the volumes and snapshots and you can only increase it by installing new hardware components i
63. sites is at your own risk IBM may use or distribute any of the information you supply in any way it believes appropriate without incurring any obligation to you Any performance data contained herein was determined in a controlled environment Therefore the results obtained in other operating environments may vary significantly Some measurements may have been made on development level systems and there is no guarantee that these measurements will be the same on generally available systems Furthermore some measurements may have been estimated through extrapolation Actual results may vary Users of this document should verify the applicable data for their specific environment Information concerning non IBM products was obtained from the suppliers of those products their published announcements or other publicly available sources IBM has not tested those products and cannot confirm the accuracy of performance compatibility or any other claims related to non IBM products Questions on the capabilities of non IBM products should be addressed to the suppliers of those products This information contains examples of data and reports used in daily business operations To illustrate them as completely as possible the examples include the names of individuals companies brands and products All of these names are fictitious and any similarity to the names and addresses used by an actual business enterprise is entirely coincidental COPYRIGHT LICE
64. ssic index jsp Help from IBM IBM Support and downloads http ibm com support IBM Global Services http ibm com services 48 IBM XIV Thin Provisioning and Space Reclamation IBM XIV Storage System Thin Provisioning and Space Reclamation Thin provisioning explored File system considerations Space reclamation examples Thin provisioning is the practice of passing logical unit number LUN sizes up to application servers without actually reserving the total physical capacity of those LUNs for data storage Thin provisioning is a popular feature of IBM XIV Storage System Data space reclamation helps you enjoy the benefits of thin provisioning Space reclamation is a storage system function to reclaim a specific amount of disk space for general purpose use after being notified by the file system that the disk space was deleted at the host level Because thin provisioning and support for space reclamation are so tightly related in the XIV storage system this IBM Redpaper publication explores both concepts in detail This publication is intended for system and storage administrators who want to take advantage of the XIV storage system functionality in thin provisioned environments coupled with the latest space reclamation enhancements REDP 5001 00 I I Illu ul TIL O INTERNATIONAL TECHNICAL SUPPORT ORGANIZATION BUILDING TECHNICAL INFORMATION BASED ON PRACTICAL EXPERIENCE IBM Redbooks are deve
65. system IBM recently announced the near future ability to migrate volumes between XIV systems Host based migration capabilities 4 1 1 Thin provisioning implementation example XIV enables you to adapt thin provisioning technology easily This section contains an example of how to plan and implement XIV thin provisioning The following procedure assumes no prior experience with XIV thin provisioning 1 Choose a non production or non business critical application as the first candidate for thin provisioning 2 Ensure that the candidate application volumes all reside in a single regular XIV storage pool An an example consider the regular XIV system storage pool named Test in Figure 4 1 Figure 4 1 Regular storage pool thin candidate Three years ago the Test group requested 20 TB of storage There is only one 3 TB XIV volume in the storage pool and it contains 2 1 TB of data The total volume sizes are 3 TB This data is basically used over and over again to test the product updates and grows by less than 1 year to year This storage pool is an ideal candidate for thin provisioning Chapter 4 Thin provisioning planning and usage 27 28 3 To change this pool from regular to thin provisioning go to the storage pool view of the XIV Management GUI right click the Test storage pool and choose Resize as shown in Figure 4 2 XIV Storage Management JE Systems Actio
66. t space to 206 GB to implement the previously mentioned guideline of 10 for snapshot space Figure 4 4 shows the new Thin Pool specifications for the Test pool Resize Pool Test XIV 7820784 O e Regular Pool e Thin Pool t M t System Allocated x Pools 15 q V 20 357 GB 107 258 GB a RJ System Free 82 Pool Hard Size 2529 GB Pool Soft Size 3803 GB Snapshots Size 206 GB Lock Behavior Read only aa E Figure 4 4 Thin pool configuration When you convert this XIV storage pool to thin provisioning 16 5 TB is returned to the total system capacity Figure 4 5 shows the XIV Management GUI view of the new thin pool Out of the total pool hard space 2 1 TB of the 2 5 TB is used which leaves 361 GB of pool hard space free Figure 4 5 New thin pool The amount of hard capacity used in the Test pool is shown in yellow because the volume usage is greater than 80 of the pool hard size However this pool s hard space was carefully sized with a knowledge of growth requirements 4 2 Thin provisioning conclusions There are several conclusions about XIV thin provisioning gt XIV thin provisioning is a mature XIV function that is fundamentally part of the XIV architecture XIV thin provisioning is easy to implement and use Using thin provisioning allows for a more efficient storage allocation strategy Chapter 4 Thin provisioning planning and usage 29 30 Ther
67. t system sees a 34 GB LUN logical unit number a 51 GB LUN and a 68 GB LUN The storage pool size is the total of all three LUNs which is 153 GB and about 40 of this storage is used In the thin pool the host system sees the same three LUN sizes and the total storage pool size is also 153 GB The difference is that the total space corresponding to unused portions of each LUN 34 GB 51 GB and 68 GB in XIV is not dedicated to those three LUNs but remains available for other storage purposes IBM XIV Thin Provisioning and Space Reclamation When you create a storage pool using thin provisioning that pool is defined in terms of both a soft size and a hard size independently as opposed to a regular storage pool in which these sizes are by definition equivalent Regular Pool Figure 2 2 Regular pool versus thin pool Hard pool size Hard pool size is the maximum actual capacity that can be used by all of the volumes and snapshots in the pool As long as there is hard system capacity available in the XIV system you can increase the hard pool size dynamically The hard pool size must always exceed the total amount of data written to all volumes in the pool Thin provisioning of the storage pool maximizes capacity utilization in the context of a group of volumes where the aggregate host apparent or soft capacity assigned to all volumes surpasses the underlying physical or hard capacity allocated to them
68. the partitions XIV storage might later mark these partitions as unused as part of the normal scrubbing process gt It might increase physical capacity usage during the process The operation is guaranteed to complete and cannot fail silently Symantec Storage Foundation employs SCSI WRITE SAME commands 5 1 3 XIV space reclamation considerations The XIV architecture is by design thinly provisioned The effectiveness of space reclamation is really dependent on how the OS interacts with the XIV architecture The smallest unit of capacity that can be freed is a partition 1 MB Although the partitions might be freed the change in physical capacity hard space might not be noticeable because the XIV GUI displays the allocation in multiples of the minimum XIV allocation size 17 GB Note XIV pool space reclamation occurs after an entire 17 GB allocation is freed because the minimum XIV allocation size for a LUN is 17 GB The use of XIV snapshots will affect the ability to reclaim space Obviously data preserved by a snapshot cannot be reclaimed because it is in use by the snapshot Other considerations include these situations gt WRITE SAME can increase snapshot space when writing zeros to data related to snapshots gt UNMAP might result in snapshots being deleted if additional pool space is needed Additional space is usually needed due to the possible delay in executing the UNMAP of unused data Note UNMAP can result in s
69. timizing storage utilization by allocating to a volume only the space required to hold its actual data deferring additional space allocation to the time that it is needed Thin provisioning is implemented on the storage level and it is transparent to the host using the volume Over provisioning is the ability to provide storage pools and volumes inside the pools with an accumulated size larger than the physical capacity available on the system The XIV storage system supports both thin provisioning and over provisioning gt Define volume sizes that are larger than the physical capacity of the of the storage pool gt Define pools and volumes within them with an accumulated size larger than the physical capacity available on the system There is little benefit to thin provisioning without over provisioning Thin provisioning is the mechanism for implementing thin provisioned storage pools This is also referred to as basic provisioning Over provisioning can only be configured by IBM support Over provisioning is referred to as advanced provisioning The concept of thin provisioning commonly covers both basic and advanced provisioning 2 1 1 Logical and actual volume sizes 10 In traditional volumes the assigned physical capacity is equivalent to the logical capacity presented to hosts This situation does not have to be the case with XIV thin provisioning For a given XIV logical volume there are effectively two associated sizes the l
70. torwize FlashSystem Redpaper System Storage IBMO Redbooks logo 48 O XIV The following terms are trademarks of other companies Linux is a trademark of Linus Torvalds in the United States other countries or both Microsoft Windows and the Windows logo are trademarks of Microsoft Corporation in the United States other countries or both UNIX is a registered trademark of The Open Group in the United States and other countries Other company product or service names may be trademarks or service marks of others vi IBM XIV Thin Provisioning and Space Reclamation Preface Thin provisioning is the practice of passing logical unit number LUN sizes up to application servers without actually reserving the total physical capacity of those LUNs for data storage Thin provisioning is a popular feature of IBM XIV Storage System Data space reclamation helps you enjoy the benefits of thin provisioning Space reclamation is a storage system function to reclaim a specific amount of disk space for general purpose use after being notified by the file system that the disk space was deleted at the host level Because thin provisioning and support for space reclamation are so tightly related in the XIV storage system this IBM Redpaper publication explores both concepts in detail This publication is intended for system and storage administrators who want to take advantage of the XIV storage system functionality in thin provisio
71. ts space reclamation on thin provisioned volumes For more information about the operating systems and VxVM versions that are supported see the System Storage Interoperability Center SSIC at http www ibm com systems support storage config ssic For more information about attaching the IBM XIV Storage System to hosts with VxVM and DMP see the Symantec website at https sort symantec com as The following tasks must be completed to successfully attach the XIV storage system to host systems by using VxVM with DMP gt Verify Array Support Library ASL availability for XIV Storage System on your Symantec Storage Foundation installation and install the XIV Host Attachment Kit gt Place the XIV volumes under VxVM control Setup DMP multipathing with IBM XIV storage Make sure that you install all the patches and updates available for your Symantec Storage Foundation installation For more information see your Symantec Storage Foundation documentation The following sections explain how you place the XIV volumes under VxVM control and how to use space reclamation Placing the volumes under VxVM control To place XIV LUNs under VxVM control complete the following steps 1 Label the disks with the format command 2 Discover new devices on your hosts by using either the vxdiskconfig or vxdisk f scandisks command 3 Check for new devices that were discovered by using the vxdisk list command as illustrated in Example 5 1
72. umes and snapshots from being exhausted Ideally hard capacity utilization must be maintained under a certain threshold by increasing the hard pool size as needed in advance Storage pools and snapshots Storage pools control when and which snapshots are deleted when there is insufficient space assigned within the pool for snapshots gt The soft snapshot reserve capacity and the hard space allocated to the storage pool are used only when changes occur to the master volumes or the snapshots themselves not when snapshots are created gt See IBM XIV Storage System Copy Services and Migration SG24 7759 for a more detailed explanation of snapshot deletion priority Soft pool size Soft pool size is the maximum logical capacity that can be assigned to all the volumes and snapshots in the pool The soft pool size must be equal to or larger than the total of the committed volume sizes in the storage pool Thin provisioning is managed for each storage pool independently of all other storage pools Regardless of any unused capacity that might be located in other storage pools snapshots within a given storage pool are deleted by the system according to the corresponding snapshot preset priority if the hard pool size contains insufficient space to create an additional volume or increase the size of an existing volume Snapshots are deleted only when a write occurs under those conditions and not when allocating more space gt As de
73. vision friendly the following general considerations apply gt Formatting the file system that is including metedata does not require allocation of a lot of space gt Writing data to the file system does not require much more space than the actual written data size gt The file system has a native reclamation method or at least efficiently reuses free space Table 3 1 summarizes file systems that can benefit the most from XIV thin provisioning Table 3 1 Systems compatible with XIV thin provisioning File system Gens thin Gen thin File system free Reclamation provision provision space reuse method compatible compatible NTFS Substantial SDelete z will be reclaimed by VMFS Yes Yes scrubbing o Not significant Storage VMotion to new VMFS and delete old VMFS VxFS Substantial vxdisk reclaim only for volumes without snapshots and mirroring mem m Desmen m There is no need to separate XIV volumes that can and cannot benefit from thin provisioning into different storage pools If there are volumes in a mixed pool that can benefit from thin provisioning make the pool a thin pool It is normally best to group XIV volumes in pools according to application boundaries As for file systems applications running on those file systems bear similar considerations in terms of being thin provisioning friendly or not Considerations include how much space is allocated up front when initially creating files or
74. w also available in Windows Server 2012 When a threshold is exceeded on the IBM XIV Storage System Gens the alerts are triggered as Windows System Event logs There is no need to configure anything for the XIV system Chapter 5 Space reclamation with XIV 35 At the OS level the Windows System Event log will report the system events shown in Table 5 2 Table 5 2 Windows events for volume usage Threshold notification without additional information Threshold notification without specific information If a permanent resource exhaustion threshold is reached the following also occurs gt A Windows System Event log ID 150 is generated gt The thin provisioned XIV volume is taken offline and becomes unavailable until the storage administrator increases the volume capacity and pool capacity Initial setup Volumes are created in a thin pool on the XIV system and are defined to a Windows 2012 Server using the XIV Host Attachment Kit Windows will recognize that these volumes are thin provisioned drives The Optimize Drives menu which is part of Windows Tools displays the space efficiency and will analyze and optimize drives as needed as illustrated in Figure 5 2 on page 37 Space reclamation automatically occurs as files are deleted or moved and the analyze option can verify the current state of the thin provisioned volumes Note that the space is not necessarily immediately reclaimed 36 IBM XIV Thin Provisioning and Space Reclamat
75. y when a host deletes files not only the host file system but also the back end storage system reclaim that space The current implementations of space reclamation in operating systems OS are typically achieved by invoking the Small Computer System Interface SCSI WRITE SAME or the SCSI UNMAP command Which commands are used depends on the operating system involved These SCSI primitive commands have different characteristics and can vary in the amount of capacity that can be reclaimed 5 1 1 UNMAP command 32 The T10 Technical Committee established the T10 SCSI Block Command 3 SBC3 specification that defines the UNMAP command for a diverse spectrum of storage devices including hard disk drives HDDs and numerous other storage media Using SCSI UNMAP IT administrators can reclaim host file system space and back end storage dead space typically within 30 seconds of a host file deletion However not only does SCSI UNMAP require T10 SBC3 compliant SCSI hardware it also requires necessary software application programming interfaces APIs Note The XIV Storage System Gen3 with Storage Software V11 2 or later is T10 SCSI UNMAP command compliant The UNMAP command has the following characteristics gt Itdeallocates a partition immediately making the capacity available to other volumes gt The operation will not increase the physical capacity used The operation is not guaranteed to complete and it can fail silently This is

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