A restore operation reverts a parent resource dataset to a previous point-in-time when a snapshot was taken. Only snapshots directly taken of the resource can be used as the source for the restore operation. When a restore operation is started, pointer updates occur, and the entire resource dataset is reverted to the previous point-in-time contained within the snapshot. Restore is supported on volumes, volume groups, file systems, and any thin clones of these resources. The restore operation is not supported on virtual machines, but users can use the Revert option in vCenter. If you restore a volume group or volume group thin clone, all member volumes are restored to the point-in-time associated with the source snapshot. More information about volume groups can be found in Snapshot interoperability.
Note: File systems that have File-Level Retention Compliance (FLR-C) enabled do not support the Restore operation.
As mentioned, a restore operation reverts the entire resource back to a previous point-in-time copy of itself. If only a select amount of data must be recovered from a volume or volume group snapshot, accessing a thin clone created using the snapshot in question avoids losing any data that is updated after the snapshot was created. If the resource is a file system or file system thin clone, accessing the protocol (read-only) snapshot through an SMB share or NFS export also avoids the Restore operation when only a subset of data is needed. Accessing file system and file system thin clone snapshots is discussed in detail in Snapshot access.
Volume shrink is not supported on PowerStore. Restoring a volume, volume group, or thin clone from a snapshot does not reduce the size of the resource even if the snapshot was taken when the resource was the previous size. Instead, the resource size remains at the current size, but with the original dataset restored. For instance, if the snapshot was taken of the parent volume when it was 500 GBs, and it is now 750 GBs, the operation restores the data to the 750 GB volume.
For file systems and thin clones, this behavior is different since file system shrink is supported. The size of the object being restored changes based on the size of the resource when the snapshot was taken. For instance, if the snapshot was taken of the parent file system when it was 100 GBs, and it is now 200 GBs, the restore operation updates the size of the resource to be 100 GBs and the original data is restored.
Issuing a restore operation for volumes, volume groups, file systems, and any thin clones of these resources can be completed multiple ways. One method is to select the resource directly within the volumes, volume groups, or file systems page within PowerStore Manager. Click Protect and select Restore from Snapshot. A window like the one shown in Figure 14 appears. As with refresh, a warning is shown to remind the user to shut down applications using the volume and take the volume offline on the hosts. These operations should be performed prior to the restore operation to prevent data integrity issues. Taking a backup snapshot is also suggested. Now, the user can select a snapshot from the list to use as the restore point. As with other operations, the option to create a backup snapshot is also provided. Selected by default, this option creates a snapshot of the current point-in-time to preserve it in case it is needed in the future.
A restore operation can also be completed from the Snapshots tab on the Protection tab within the properties of the resource. Using this method, the user can select which snapshot to restore from, then select More Actions, and lastly Restore from Snapshot. A window similar to the one displayed in Figure 14 is shown, and the snapshot that was previously selected is automatically checked. After the Restore button is selected and before the operation starts, the user is provided with a confirmation window similar to the one shown in Figure 15. The user can then click Restore to take a backup snapshot and restore the parent object.