Dell PowerVault ME4 Series Storage System Administrator’s Guide

About snapshots

The system can create snapshots of virtual volumes up to the maximum number supported by your system. Snapshots provide data protection by enabling you to create and save source volume data states at the point in time when the snapshot was created. Snapshots can be created manually or you can schedule snapshot creation. After a snapshot has been created, the source volume cannot be expanded.

When you reach the maximum number of snapshots for your system, before you can create a new snapshot, you must delete an existing snapshot. To view the maximum number of snapshots for your system, see the System configuration limits topic in the PowerVault Manager help.

The system treats a snapshot like any other volume. The snapshot can be mapped to hosts with read-only access, read-write access, or no access, depending on the purpose of the snapshot.

Snapshots use the rollback feature, which replaces the data of a source volume or snapshot with the data of a snapshot that was created from it.

Snapshots also use the reset snapshot feature, which enables you to replace the data in a snapshot with the current data in the source volume. When you reset a snapshot, the snapshot name and mappings are not changed.

The set snapshot-space CLI command enables you to set the percent of the pool that can be used for snapshots (the snapshot space). Optionally, you can specify a limit policy to enact when the snapshot space reaches the percentage. You can set the policy to either notify you via the event log that the percentage has been reached (in which case the system continues to take snapshots, using the general pool space), or to notify you and trigger automatic deletion of snapshots. If automatic deletion is triggered, snapshots are deleted according to their configured retention priority. For more information, see the Dell PowerVault ME4 Series Storage System CLI Guide.