Static target allocation

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When you use SAN Volume Controller and Storwize® family, IBM® Storage Protect Snapshot software can restore FlashCopy® backups before completion of a background copy.

When you restore snapshot backups before completion of a background copy, space-efficient volumes can be enabled as backup targets. The background copy rate is set to zero to prevent the snapshot target from becoming fully allocated. When you use either SAN Volume Controller or Storwize family, and IBM Storage Protect Snapshot software in this scenario, use the following guidelines for the environment:
Physical capacity
The physically allocated capacity of a space-efficient target volume must be large enough to contain all changes that occur to your production environment. Specifically, all changes that occur between the current and the subsequent backup. If the capacity is insufficient, the target volume goes offline and the corresponding backup becomes invalid.
SAN Volume Controller and Storwize family support the creation of automatically expanding target volumes. If you create target volumes that automatically expand, more storage is assigned to the target when the level of unused real volume capacity decreases. This additional storage ensures that sufficient capacity is available.
Tip: If you select SAN Volume Controller and Storwize family dynamic target allocation, all target volumes that were created dynamically will be auto-expandable.
FlashCopy relationships
During a restore, IBM Storage Protect Snapshot software stops FlashCopy relationships. These relationships include relationships that are established at the time when the backup is created to any subsequent relationships that are created on the same source LUN. All backups to space-efficient targets that are newer than the backup used for restore, and the backup from which you are restoring, are deleted. If the background copy was not completed, the same restriction applies to full and incremental FlashCopy backups.

To check whether a backup is going to be deleted, query the usability state of IBM Storage Protect Snapshot backups. If the backup is going to be deleted, during the restore process, the DESTRUCTIVELY_RESTORABLE state is set. Otherwise, the state is set to REPETITIVELY_RESTORABLE.

Important: This does not apply if you select SAN Volume Controller and Storwize family dynamic target allocation. With SVCDTA, no backups are deleted during a restore operation.
Target sets
IBM Storage Protect Snapshot cannot reuse a target set for a new snapshot backup unless it corresponds to the last snapshot mapping in a cascaded snapshot relationship. This scenario implies that when IBM Storage Protect Snapshot reuses a target set, all backups that are created before this point in time are deleted. In a non-mirrored environment, all backups that are created before this point in time are deleted when the following conditions are met:
  • The same profile for the IBM Storage Protect Snapshot backups is used.
  • This profile contains only one DEVICE_CLASS statement in the CLIENT section.
In an LVM mirrored environment, all backups that are created before this point in time are deleted when the CLIENT section of the profile contains one DEVICE_CLASS statement for each LVM mirror. If multiple device classes are specified within this statement, each device class must manage the same number of target sets.
Important: This does not apply if you select SAN Volume Controller and Storwize family dynamic target allocation.

Recommendations for setting up the environment with static target volumes

When you set up the SAN Volume Controller and Storwize family environments for use with IBM Storage Protect Snapshot software, the following list identifies guidelines for the environment:
  • If space-efficient source volumes are used in combination with space-efficient target volumes, IBM Storage Protect Snapshot can be configured to use FLASHCOPY_TYPE COPY, INCR, or NOCOPY. If fully allocated source volumes are used in combination with space-efficient target volumes, then IBM Storage Protect Snapshot can be configured to use FLASHCOPY_TYPE NOCOPY only.
  • Decide whether you want to use space-efficient or fully allocated backup targets. In mirrored environments, a different choice can be made for each mirror.
  • For each mirror, use one DEVICE_CLASS statement for disk-only backups. In addition, use one DEVICE_CLASS statement for dual backups. A dual backup is a disk backup and tape backup. Make sure that the schedule is defined so that the target sets are reused cyclically across both device classes per mirror.
    For example:
    • Define three target sets in the DISK_ONLY device class. Schedule these disk only backups to occur at 6:00, 12:00, and 18:00.
    • Define one target set in a DUAL_BACKUP device class. Set this schedule to create a disk and IBM Storage Protect backup at 00:15.
    If the value for the profile parameter MAX_VERSIONS is set to ADAPTIVE all disk-only backups taken before that point in time are deleted. Otherwise, the version policy causes the dual backup to fail if MAX_VERSIONS specifies seven versions.
  • If a backup that is characterized as DESTRUCTIVELY_RESTORABLE is restored, the backup you are restoring and all backups that are taken after that point in time are deleted. The backup is not deleted when the backup is created with FLASHCOPY_TYPE FULL or INCR, and the background copy completed.