Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 265

How quickly you can replicate the recovery volume depends on the presence of the failback snapshot on the primary group. The failback snapshot establishes the failback baseline, which is the point in time at which the volume on the primary group and the most recent complete replica on the secondary group have the same data. If the failback snapshot exists, only the changes made to the recovery volume are replicated. If the failback snapshot does not exist, the first replication is a complete copy of the recovery volume data. • Moving a failback replica set to a different storage pool - You can move a failback replica set to a different pool in the primary group. Later, if you promote the failback replica set to a volume, the volume belongs to the new pool. • Failing back to the primary group - To return to the original volume replication configuration, you can use the Failback to Primary operation. Recommendation: Dell recommends that you use the Replicate to Partner operation before failing back to the primary group. Although the Failback to Primary operation performs a final replication, the recovery volume is offline during the final replication. As part of the failback operation, a replica is created immediately on the secondary group to reestablish the failback snapshot (and set the failback baseline). Because the volume data is already synchronized between the groups, no data is actually transferred. Restriction: You cannot fail back a template volume. Also, the Failback to Primary operation is available only if the primary group and the secondary group are running PS Series firmware version 5.0 or greater. • Making a temporary volume available on the secondary group - You can make a temporary copy of a volume available on the secondary group, while providing continuous access to the original volume on the primary group. Using a temporary copy is helpful when you want to perform an operation (such as a backup) on the copy with no disruption to users. When the operation completes, you can resume replicating the volume. NOTE: This procedure assumes that the volume does not change while available on the secondary group, or - if the volume changes - those changes are not replicated to the primary group. If you want to replicate changes, follow the procedure described in About Failing Over and Failing Back a Volume. • Switching partner roles - You can switch the partner roles in a volume replication configuration. The original secondary group becomes the new primary group, and the original primary group becomes the new secondary group. NOTE: Because you cannot permanently demote a template volume, when you switch roles for a replication configuration that includes a template volume with thin clone volumes, only the thin clone replication configuration switches. Therefore, the original template volume must still exist on the original primary group after the switch, because the new thin clone replica sets depend on the template volume. • Making promotions permanent - After promoting an inbound replica set to a recovery volume, you can make the promotion permanent, resulting in a new standard volume, template volume, or thin clone volume. You might need to perform this task if the original volume is destroyed or if you are switching roles in a replication configuration. NOTE: After making an inbound replica set promotion permanent, you can no longer demote the volume to the original inbound replica set. Restriction: Before you can make a template replica set promotion permanent, you must permanently promote all the attached thin clone replica sets. About Recovering Data from a Snapshot You can restore a volume from a snapshot, and replace the data in the current volume with the volume data at the time you created the snapshot. The restored volume has the same name and iSCSI target name as the original volume. You can also clone a snapshot to create a new volume, allowing you to access the volume's data as it existed at a certain point in time without having to replace the volume's current data. Cloning a snapshot is especially useful if you need to recover individual files and roll them back to a previous revision. In both cases, the snapshot still exists after the restore operation. Requirements and Restrictions • To restore a volume from a snapshot, all group members containing data from the volume or its snapshots must be online. About Data Recovery 265