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Always On - why No failover occurred?

  • September 20, 2021 at 10:28 am

    #3931088

    Hi,

    I am using SQL 2016 (13.0.5888.11).

    Last Saturday (18th September), in non-office hours, my SQL Server Always On Availability Group got much errors, from the primary server's Event Viewer, I see:

    1480 - The availability group database "xxxxx" is changing roles from "PRIMARY" to "RESOLVING" because the mirroring session or availability group failed over due to role synchronization.

    41049 - Always On Availability Groups: Local Windows Server Failover Clustering node is no longer online.

    41092 - Always On: The availability replica manager is going offline because the local Windows Server Failover Clustering (WSFC) node has lost quorum.

    However, some how it started by itself, .........

    41110 - Always On: The availability replica manager is starting.

    In the morning, when we came back to office, I found the SQL Server runs as normal no role fail over occurred.

    My Session-Timeout : 10 seconds (default).

    I can't explain these to my colleagues.

    1. Why no failover occurred?
    2. Did it really no failover during the non-office hours?
    3. If there is a role switch, I can find it out from Event Viewer, but in my case, I couldn't.

    Can you help me? Thanks a lot.

  • September 20, 2021 at 5:17 pm

    #3931231

    If the secondary node was restarted - or unavailable, that would cause the kinds of messages you are seeing.  As for the cluster shutting down, it shows that the cluster lost quorum - and why that occurred depends on how you have the cluster configured.  To maintain quorum - there needs to be more than 50% quorum votes, so if you have 2 nodes and no witness - a single node being restarted will leave you with 50% votes which is not more than 50% and the cluster shuts down.

    Now if you have a witness - then you would have to lose both the witness and the node before losing quorum, and that all depends on what witness method you are using and what caused the outage to the node and witness.

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