Dell Storage Manager 2020 R1 Administrator's Guide

Managing Snapshots

Snapshots are read-only, point-in-time copies of NAS volume data. Storage administrators can restore a NAS volume from a snapshot if needed. In addition, clients can easily retrieve files in a snapshot, without storage administrator intervention.

Snapshots use a redirect-on-write method to track NAS volume changes. That is, snapshots are based on a change set. When the first snapshot of a NAS volume is created, all snapshots created after the baseline snapshot contain changes from the previous snapshot.

Various policies can be set for creating a snapshot, including when a snapshot is to be taken and how long to keep snapshots. For example, mission-critical files with high churn rates might need to be backed up every 30 minutes, whereas archival shares might only need to be backed up daily.

If you configure a NAS volume to use VM-consistent snapshots, each snapshot creation operation such as scheduled, manual, replication, or NDMP automatically creates a snapshot on the VMware server. This feature enables you to restore the VMs to the state they were in before the NAS volume snapshot was taken.

Because snapshots consume space on the NAS volume, ensure that you monitor available capacity on the NAS volume and schedule and retain snapshots in a manner that ensures that the NAS volume always has sufficient free space available for both user data and snapshots. Also, to be informed when snapshots are consuming significant NAS volume space, enable a snapshot consumption alert.

The FluidFS cluster automatically deletes one or more snapshots for a NAS volume in the following cases:

• If you delete a NAS volume, the FluidFS cluster deletes all of the snapshots for the NAS volume.
• If you restore a NAS volume from a snapshot, the FluidFS cluster deletes all the snapshots created after the snapshot from which you restored the NAS volume.