Using snapshot schedules in a DAG


Using snapshot schedules in a DAG
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In an Exchange 2010 DAG, you may want to create snapshot schedules on the replication (passive) nodes of the DAG as well as the active node. The VSS Schedule Snapshot wizard supports scheduling snapshots on passive copies.

Note:

The Quick Recovery Configuration Wizard does not support snapshots for a passive copy. If the active database copy switches to another node, a Quick Recovery Wizard schedule on the node that is now passive is no longer valid and scheduled snapshot operations on the passive node will fail.

For example, if the DAG contains an active database on NodeA that is being replicated to NodeB, you can set up a snapshot schedule on NodeB as well as on NodeA. Setting up a snapshot schedule on the replication node ensures that snapshots continue as scheduled if a database fails on the active node.

Exchange 2010 provides two VSS Writers as follows:

The Store Writer is available on any mailbox server and is used for backup and restore of active databases.
The Replication Writer is available on the passive node of a DAG server. The Replication Writer supports backup functionality for a selected database where the snapshot is taken against the replicated instance of the database and transaction log files. The Replication Writer is supported by SFW Flashsnap for snapshot and schedule snapshot operations but not for restore operations.

If you have set up schedules on both the active and passive nodes, the appropriate VSS writer is used automatically for the scheduled snapshot. For example, if the database on NodeA changes from an active to a passive copy, the snapshot schedule is maintained with the Replication Writer if the database remains in a healthy state. If you have set up a snapshot schedule on NodeB and the database on NodeB changes from a passive to an active copy, the snapshot schedule on NodeB continues using the Store Writer.