Database Availability Group Failover During a Mailbox Move

During a mailbox move operation if the active database becomes unavailable then the Mailbox Replication Service [MRS] contacts the active manager to see which copy will take over. MRS then logs on to the mailbox on the new database and continues with the move process from where it left off. This as long as the DataMoveReplicationConstraint setting for the database is set to something else other than None and as long as the database was not down for longer than 30 minutes (or there is another copy satisfying the constraint).

Let us assume the database has 3 copies. It is entirely possible that MRS will just continue working after a failover even if the original server is down.

If DataMoveReplicationConstraint is set to None then MRS will try to connect to the same database every 30 seconds for the next 30 minutes. The 30 minute is from the maximum retry of 60 times every 30 seconds. This value can be changed in the in the msExchMailboxReplication.exe.config file.

The DataMoveReplicationConstraint parameter specifies the throttling behavior for high availability mailbox moves. The possible values are:

    • None: moves should not be throttled to ensure high availability. Use this setting if the database is not part of a DAG;
    • SecondCopy (default): at least one passive mailbox database copy must have the most recent changes synchronized. Use this setting to indicate that the database is replicated to one or more mailbox database copies;
    • SecondDatacenter: at least one passive mailbox database copy in another AD site must have the most recent changes replicated. Use this setting to indicate that the database is replicated to database copies in multiple AD sites;
    • AllDatacenters: at least one passive mailbox database copy in each AD site must have the most recent changes replicated. Use this setting to indicate that the database is replicated to database copies in multiple AD sites;
    • AllCopies: all copies of the database must have the most recent changes replicated. Use this setting to indicate that the database is replicated to one or more mailbox database copies.

Note: any value other than None enables MRS to coordinate with Active Manager.

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