IBM XIV Storage System Copy Services and Migration

Figure 1-19 illustrates selecting the Restore action on the ITSO_Volume volume.Figure 1-19 Snapshot volume restoreAfter you perform the restore action, you return to the Volumes and snapshots panel. Theprocess is instantaneous, and none of the properties (creation date, deletion priority, modifiedproperties, or locked properties) of the snapshot or the volume have changed.Specifically, the process modifies the pointers to the master volume so that they areequivalent to the snapshot pointer. This change only occurs for partitions that have beenmodified. On modification, the XIV Storage System stores the data in a new partition andmodifies the master volume’s pointer to the new partition. The snapshot pointer does notchange and remains pointing at the original data. The restoration process restores the pointerback to the original data and frees the modified partition space.If a snapshot is taken and later on the original volume increases in size, you can still do arestore operation. The snapshot still has the original volume size and when you restore it tothe original volume this volume also will have the original size again.The XCLI Session (or XCLI command) provides more options for restoration than the GUI.With the XCLI, you can restore a snapshot to a parent snapshot (Example 1-4).Example 1-4 Restoring a snapshot to another snapshotsnapshot_restore snapshot=ITSO_Volume.snapshot_00002target_snapshot=ITSO_Volume.snapshot_000011.2.5 Overwriting snapshotsFor your regular backup jobs you can decide whether you always want to create newsnapshots (and let the system delete the old ones) or whether you prefer to overwrite theexisting snapshots with the latest changes to the data. For instance, a backup applicationrequires the latest copy of the data to perform its backup operation. This overwrite operationmodifies the pointers to the snapshot data to be reset to the master volume. Therefore, allChapter 1. Snapshots 15