Quorum failure is a more complicated situation that is generally caused by persistent communications failure or by the problematic configuration of cluster nodes. Quorum failure must be resolved manually by performing the following steps:
- Start the Windows Server Failover Cluster by using forced quorum on a single node.
- You do this by choosing Force Cluster Start from the Actions pane of the Failover Cluster Manager.
- Start the Windows Server Failover Cluster service on additional nodes that can communicate with the node you started by using forced quorum.
- Configure a new quorum mode and node vote configuration that reflect the realities of the quorum topology. For example, if two nodes are frequently unavailable due to persistent communication failure, reconfigure the quorum mode and vote assignments to remediate this problem
Identify the Cause
- Determine if the quorum failure is due to storage disruption, cluster node failures, or network issues.
- Check Cluster Configuration: Make sure the Windows cluster is online and has enough voting nodes to achieve quorum.
- Force Quorum: If necessary, force quorum on the WSFC cluster to bring it online.
- Force Failover: For each availability group, force failover to make sure the databases are accessible.
Forcing failover can lose data (NEEDS APPROVAL). Any transactions not yet hardened on the target replica are lost. Afterwards, data movement on the other replicas is suspended and must be resumed.
-- Run on the replica that will become the primary
ALTER AVAILABILITY GROUP [YourAGName] FORCE_FAILOVER_ALLOW_DATA_LOSS;
Storage Disruption: Issues such as SAN connectivity problems can lead to quorum loss.
Cluster Node Failures: If nodes in the cluster restart or lose communication, it can result in quorum failure.
Network Issues: Problems with network connectivity can impact communication between cluster nodes, leading to quorum loss.
CSV Arbitration Issues: Failures in Cluster Shared Volumes (CSV) arbitration can also cause quorum loss
From my SQL Server DBA handbook.