Release Notes

19 Dell PS Series Snapshots and Clones: Best Practices and Sizing Guidelines | BP1027
4 Backup and recovery operations
4.1 Restoring from a snapshot
There are times when data in the base volume needs to be restored to a particular point in time. PS Series
snapshots provide several quick restore options to maximize the availability of critical data.
• A full volume can be quickly restored by setting a snapshot online (the host server must be powered
off or the volume must be set offline before doing this).
• A snapshot volume can be mounted to the same or another host server to allow for manual recovery
of an entire volume, a single file, or simply for verification or test and development use.
The restored volume will contain all of the data that existed in the volume at the time the snapshot was
created and have the original volume name and iSCSI target name. During the restore operation, the base
volume and the snapshot must be dismounted from the host. For example, on a Windows 2012 R2 host, the
Disk Management utility can be used to mark the volume offline or a host may be shut down or powered off
while the snapshot is restored. When a volume is restored from snapshot, Dell EqualLogic Group Manager
sets the base volume and snapshot offline for the array and, by default, returns the volume back online when
completed. Another snapshot is automatically created to preserve the contents of the volume prior to when it
was restored.
All array members that contain data from the base volume or the snapshot must be online to restore the
volume from the snapshot.
4.2 Restoring from a clone volume
A clone volume can also be used for restoring an entire volume or a single file. The clone volume can be
attached in place of the original volume (for example, if it becomes corrupt, or infected with a virus) or it can
be mounted on another host. Once mounted on another host, an administrator can then manually restore as
many files as needed to the original volume while the original volume remains online.
4.3 Deleting volumes, snapshots, and clones
If a volume is deleted, the snapshots associated with the base volume are also deleted. Users can delete the
snapshots manually if they no longer need the snapshot data or wish to reduce the number of snapshots for
the volume. In addition to this, the PS Series group can delete snapshots automatically in the following
scenarios:
• If creating another snapshot would exceed the snapshot reserve space, then the group will delete the
oldest snapshot in order to create a new snapshot.
• If a scheduled snapshot reaches the maximum number of snapshots, as specified by the schedule
keep count, the oldest snapshot created by the schedule will automatically be deleted before a new
snapshot is created.
Deleting a clone volume does not affect the original base volume. Each clone volume is independent of the
originating base volume.