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What to do when your Always On cluster loses quorum?
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Problem
I was reviewing our company DR procedures and when I looked online for solutions to an Always On Cluster losing quorum, to compare to. I was three pages into google results before finding the first SE post on the subject Clustering vs. transactional replication vs. availability groups which only lightly touches on the subject of lost quorum.
While everyone agrees the losing quorum is bad, and there are some suggestions for decreasing the potential, it can still happen. I am looking for a good peer reviewed answer to the best path to recovery from an Always On cluster loss of quorum.
While everyone agrees the losing quorum is bad, and there are some suggestions for decreasing the potential, it can still happen. I am looking for a good peer reviewed answer to the best path to recovery from an Always On cluster loss of quorum.
Solution
AGs are based on Windows Clustering. The WSFC procedures for quorum loss apply.
Once the WSFC is running, you can then force AG, if needed. Perform a Forced Manual Failover of an Availability Group:
After forcing quorum on the WSFC cluster (forced quorum), you need to force failover each availability group (with possible data loss). Forcing failover is required because the real state of the WSFC cluster values might have been lost. However, you can avoid data loss, if are able to force failover on the server instance that was hosting the replica that was the primary replica before you forced quorum or to a secondary replica that was synchronized before you forced quorum. For more information, see Potential Ways to Avoid Data Loss After Quorum is Forced.
- WSFC Disaster Recovery through Forced Quorum
- Force a WSFC Cluster to Start Without a Quorum
Once the WSFC is running, you can then force AG, if needed. Perform a Forced Manual Failover of an Availability Group:
After forcing quorum on the WSFC cluster (forced quorum), you need to force failover each availability group (with possible data loss). Forcing failover is required because the real state of the WSFC cluster values might have been lost. However, you can avoid data loss, if are able to force failover on the server instance that was hosting the replica that was the primary replica before you forced quorum or to a secondary replica that was synchronized before you forced quorum. For more information, see Potential Ways to Avoid Data Loss After Quorum is Forced.
Context
StackExchange Database Administrators Q#125915, answer score: 11
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