Process to failback after an AG failover using asynchronous mode

  • I'm testing the failover process in my AG that is using Asynchronous availability mode.  In the scenario where I manually failover from Server A (primary) to B, what is the process to fail back to A?  It seems like the only way is to rebuild the entire synchronization from B to A, failover to A, and then repeat the synch rebuild.

    In synchronous mode, manual failovers are a breeze since the synch process resolves itself after the failover, but asynch doesn't behave that way in my environment.  Is this expected?

  • In a two-node AG you should have Primary and a sync secondary. As you have said, failover is easy because the secondary is sync. When you failover, both nodes will still be in sync mode - the minimum configuration, as far as I know,  is one sync secondary.

    If you have several nodes and need to failover to an async secondary you can either set it to sync first, or you can force the failover and accept the possibile risk of data loss.

    https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/perform-a-forced-manual-failover-of-an-availability-group-sql-server?view=sql-server-ver15

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