2 Node Highly Available SQL Cluster

You need to first understand the role of quorum. A quorum means consensu, to reach on that consensus you need votes. The WSFC works in such a way that it always tries to make voting members count to ODD number. In you case you have 2 nodes so 2 voting members which is even so not a good candidate to form proper quorum is a node goes down. Now If you add one FS witness or disk as voting member a odd number voting members will be formed and even when one node is down 2 nodes will be voting making quorum possible. For quorum to be possible the number o voting members anytime should be > 50 %. In your case with 2 nodes and with one node going down it will be less < 50 % so no quorum and WSFC will come down. Please read understanding Cluster Quorum

Does it need 2 Quorums, one for windows as a shared disk, and another for SQL?

SQL Server has no work deciding quorum, its WSFC who is affected by quorum. So you just need 1 quorum at WSFC level to make sure even with nodes going down unexpectedly WSFC is online.

SQL Server doesn't need a separate quorum resource. It relies on the cluster for that. And for a SQL Server Failover Cluster Instance storing the databases on a Shared Disk you should use a Disk Witness.

Hi @create share ,

Does it need 2 Quorums, one for windows as a shared disk, and another for SQL?

No. You just need one quorum. Because SQL Server AlwaysOn availability Group is based on WSFC, and a shared disk is one kind of quorum mode, it is configured at the WSFC cluster level that dictates the methodology used for quorum voting. You can understanding as next:

Step1: WSFC (NODES, Witness)--If you have two nodes, a witness is required.
Step2:AlwaysOn availability Group

More information: understand-quorum, wsfc-quorum-modes-and-voting-configuration-sql-server

BR,
Mia

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Hi @create share ,

Is the reply helpful?

BR,
Mia

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