Dell PowerVault ME4 Series Storage System Administrator’s Guide

Primary volumes and volume groups

The volume, volume group, or snapshot that will be replicated is called the primary volume or volume group. It can belong to only one replication set. If the volume group is already in a replication set, individual volumes may not be included in separate replication sets. Conversely, if a volume that is a member of a volume group is already in a replication set, its volume group cannot be included in a separate replication set.

The maximum number of individual volumes and snapshots that can be replicated is 32 in total. If a volume group is being replicated, the maximum number of volumes that can exist in the group is 16.

Using a volume group for a replication set enables you to make sure that the contents of multiple volumes are synchronized at the same time. When a volume group is replicated, snapshots of all of the volumes are created simultaneously. In doing so, it functions as a consistency group, ensuring consistent copies of a group of volumes. The snapshots are then replicated as a group. Though the snapshots may differ in size, replication of the volume group is not complete until all of the snapshots are replicated.