Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 264

17 About Data Recovery A PS Series group is part of a comprehensive backup and data protection solution. Snapshots provide quick recovery and offloading backup operations. Restore operations are more reliable because snapshots ensure the integrity of the backed-up data. Replication protects data from serious failures such as destruction of a volume during a power outage, or a complete site disaster. The following list provides more information: • Snapshots - You can use a snapshot to restore a volume to the state it was in at the time the snapshot was created. In addition, you can make snapshots available to iSCSI initiators or clone the snapshot to create a new volume. • Setting snapshots online or offline - By default, a snapshot is offline. You can set a snapshot online, making it accessible to iSCSI initiators that match one of the snapshot's access control policies.If you set a snapshot offline, any current iSCSI connections to the snapshot are lost. • Cloning snapshots to create volumes - Cloning a snapshot creates a new standard volume, template volume, or thin clone volume with a new name and new iSCSI target name, but with the same reported size, pool, and contents as the original volume at the time that you created the snapshot. The group allocates space equal to the volume reserve that you specify for the new volume. If you reserve snapshot space for the new volume, the group allocates additional space. The snapshot still exists after the clone operation. • Restoring a volume 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 snapshot still exists after the restore operation. • Replicas - You can use replicas to recover data on a volume in several ways: - Failing over a volume to its replica, and later failing back to the primary group. - Promoting a replica to a recovery volume and replicating its data back to the primary group. You can later demote the volume and resume the original replication, or you can make the promotion permanent. - Moving a replica set to another storage pool. - Switching partner roles so that the primary group is now the secondary group and vice versa. • Promoting an inbound replica set to a recovery volume - To temporarily fail over a volume (or template or thin clone) to the secondary group, you promote the inbound replica set to a recovery volume (or recovery template or recovery thin clone) and snapshots. Users can connect to the recovery volume and resume accessing the volume data. A recovery volume name is generated automatically, based on the volume name, with a dot-number extension (for example, vol01.1). You can choose to keep the same iSCSI target name as the original volume to facilitate iSCSI initiator connections to the recovery volume. Promoting an inbound replica set does not require any additional space on the secondary group, because it reduces delegated space by the size of the volume's replica reserve. Thin provisioning is automatically enabled for recovery volumes. • Replicating a recovery volume to the primary group - When the original volume on the primary group becomes available, you can replicate the recovery volume to the primary group. This action synchronizes the data across both groups and protects the recovery volume. During the replication, initiators can continue to access the recovery volume. Recommendation: Dell recommends that you replicate the recovery volume to the primary group immediately before failing back to the primary group, because the volume is offline during the final replication that is part of failing back to the primary group. Restriction: You cannot replicate a recovery template volume. The Replicate to Partner operation is available only if the primary group and the secondary group are running PS Series firmware version 5.0 or greater. If you do not meet this requirement, you must perform the steps individually. 264 About Data Recovery