Tivoli® Storage FlashCopy® Manager exploitation of SAN Volume Controller and Storwize® V7000 FlashCopy capabilities on Windows are dependent on the Volume Shadow Copy Service (VSS) hardware provider for SAN Volume Controller and Storwize V7000.
Configuration of the VSS provider for SAN Volume Controller and Storwize V7000 controls what type of FlashCopy is run when a VSS snapshot is requested. It also controls the behavior that results when you use VSS snapshots.
The VSS provider that supports SAN Volume Controller and Storwize V7000 has the following characteristics:
In this scenario, deleting the VSS snapshot removes it from the VSS inventory, but the FlashCopy relationship remains with the SAN Volume Controller and Storwize V7000. A subsequent VSS snapshot of the same source volume results in an incremental refresh of the target volume.
The deletion of a VSS snapshot, that is represented by a target volume in a cascade, also causes all target volumes that are dependent on the volume that is being deleted (that is, the target volumes that were created earlier) to be deleted. For example, the deletion of a snapshot that is represented by target volume T2 in the sample cascade S -> T4 -> T3 -> T2 -> T1 causes T2 and T1 to be deleted. The cascade S -> T4 -> T3 remains after the deletion.
When you manually delete backups on the SAN Volume Controller and Storwize V7000 space-efficient target volumes, and multiple backup versions exist, the backup that is being deleted, and any older backups that contain the same volumes are deleted. The deletion might not occur until the next snapshot operation.
A FlashCopy restore of the source volume from a target volume in a cascade of multiple target volumes is destructive to the target volume that is being restored and to all newer targets in the cascade. For example, the restore of a snapshot that is represented by target volume T3 in the sample cascade S -> T4 -> T3 -> T2 -> T1 causes T4 and T3 to be deleted. The cascade S -> T2 -> T1 remains after the restore.
One exception to this pattern is that a FlashCopy restore from an space-efficient target that is the only target in the cascade is not destructive.
A space-efficient backup version is defined by a FlashCopy to an space-efficient target volume that has a background copy rate of zero. The use of space-efficient target volumes with the autoexpand option that is enabled and a background copy rate set to greater than zero does not create space-efficient backup versions. The target volumes grow to the allocated size of the source volumes when the background copy completes.
Given these characteristics, the following requirements apply to Tivoli Storage FlashCopy Manager support of SAN Volume Controller and Storwize V7000:
A transition from fully allocated targets to space-efficient targets is accommodated by treating fully allocated targets as if they were space-efficient when the background copy rate is set to 0.
Do not mix persistent and nonpersistent VSS snapshots. Use of a nonpersistent VSS snapshot that follows one or more persistent snapshots causes the older persistent snapshots to be deleted when the nonpersistent snapshot is deleted.
A VSS backup with backupdestination set to TSM creates a nonpersistent VSS snapshot. Therefore, do not follow a series of backups to local with backupdestination set to TSM. Instead, set backupdestination to both to send data to Tivoli Storage Manager while it preserves local snapshot backup versions. The settings backupdestination=LOCAL and backupdestination=TSM are mutually exclusive. Do not use both in a backup strategy.
Tivoli Storage FlashCopy Manager supports VSS instant restore operations when multiple backup versions exist on SAN Volume Controller and Storwize V7000 space-efficient target volumes.
However, in this situation, VSS instant restore accesses snapshot volumes that contain dependent FlashCopy relationships. The snapshot volumes that create the dependency are typically backups that are created after the snapshot that is being restored. These snapshot volumes are removed for the VSS instant restore operation to complete successfully. The backups that included the deleted snapshots are deleted from storage. This destructive restore operation occurs only when VSS instant restore operations occur in an environment where Tivoli Storage FlashCopy Manager manages multiple backup versions on SAN Volume Controller and Storwize V7000 space-efficient target volumes.
When multiple backup versions exist, all snapshots that are newer than the snapshot that is being restored are deleted during the VSS instant restore operation. The snapshot that is being restored is also deleted. When only one snapshot backup version exists, the snapshot that is being restored is not deleted.