Home > Storage > PowerMax and VMAX > Data Protection > Dell EMC PowerMax and VMAX All Flash: TimeFinder SnapVX Local Replication > SnapSet and SnapSet ID
A SnapSet is a set of consistent snapshots that are taken together across a group of volumes. For example, when a snapshot is taken of an SG that contains 10 devices, the resulting SnapSet consists of 10 consistent snapshots.
Beginning with the PowerMaxOS Q3 2020 release, snapshots are assigned a SnapSet ID. The SnapSet ID is an absolute value that remains the same regardless of creation or deletion of other snapshot generations. When a snapshot is taken across a SnapSet, the snapshots that are created on the individual TDEVs in the SnapSet have the same SnapSet ID. SnapSet IDs are assigned to all snapshot types.
The following figure shows the SnapSet ID of a snapshot.
The generation ID of a snapshot is relative to the number of snapshots at the time the snapshots are viewed. However, the SnapSet ID remains the same throughout the life of the snapshot. Since the introduction of SnapVX, the standard method to control or view details of a snapshot is to use the relative generation number, and this method continues to be supported.
However, using snapshot policies can increase the snapshot frequency and snapshot count. This usage also increases the probability that the relative generation number is changed shortly before the user issues a control command to a snapshot. This scenario would issue the control command to the incorrect snapshot.
Creating and terminating snapshots on subsets of the devices in a group could also cause snapshots of the group to have different generation IDs on the individual snapshots. The SnapSet ID would remain constant.
The best practice is to use the SnapSet ID rather than the generation ID. We do not recommend correlating the SnapSet ID of a snapshot to the generation ID. The generation ID will change the next time another snapshot is created and or terminated.