Considerations for DAGs

  • Catalogic DPX always follows the active database in a DAG. Although Exchange is located on each physical node of the DAG, the Exchange application disk EXCH is only visible under the virtual node. At the time of backup or restore, the source or target used depends on what is currently active in the DAG.

  • When adding an IP-less DAG, use IP address 255.255.255.255. An IP-less DAG is also referred to as an Exchange DAG with no administrative access point.

  • When adding DAG cluster nodes, ensure all clusters nodes are online.

  • Catalogic DPX backs up Exchange DAG mailboxes from active and passive databases. The Microsoft recommendation to back up from passive databases is intended to eliminate CPU and I/O load on the active server and is reasonable for traditional File backup methods. However, Block backups have minimal impact on the backup source node. The Catalogic DPX Block Data Protection’s proven, block-level technology enables safe, non-intrusive backup of active databases, which has significant benefits:

    • Backing up the active copy guarantees that the most up-to-date Exchange data is captured.

    • Backups are from an active functioning Exchange database and don’t rely on successful replication to the passive copy.

Note. Bare Metal Recovery or Instant Virtualization backs up the entire physical machine, whether the Exchange database is active or passive. Such backups are independent of any Microsoft Exchange Server backups in the Catalogic DPX Block Data Protection. For information on Bare Metal Recovery, see Chapter 13: Bare Metal Recovery. For information about Instant Virtualization, see Restoring virtual machines.

  • If failover of an Exchange database occurs before a backup starts, the backup will fail in cases where the Exchange database was specifically selected for backup. The backup fails because the backup job is attempting to connect to an Exchange database that is no longer active on the server that was hosting the database when the backup was defined. If a backup fails as a result of database failover, do either of the following:

    • Define a new backup job to back up the database that is now active on the failover node. Note that defining a new backup job results in a Base backup.

    • Use Exchange Management Console to bring back the database on the original node, then rerun the backup.

    In cases where the Exchange application disk or the entire virtual node was selected for backup, the backup will follow the active database and the backup will succeed.

  • If a BMR backup is performed on a volume containing a DAG, the restore screen will display a BMR object under the DAG; however, this BMR object can not be used to restore the DAG. DAG nodes are restored individually, as for any other physical node.

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