I have two SQL 2016 servers configured in a mirror with a witness. We've been running some failover tests and every test has succeeded except the following two scenarios. Does anyone know why these scenarios wouldn't result in a failover?
- Dismounting the storage that the database files reside on the primary server will not fail the server over. I thought the witness would notice that the files do not exist anymore and fail over?
- Throttling the network down to 1kbps on the primary server disconnects the mirror on both the primary and secondary. I would think that the witness would lose connectivity to the primary because the network is so slow and fail over but instead both servers go to disconnected status.
Has anyone ran into any of these issues?
Partial answer:
(1) Dismounting disk does not cause failover because mirroring doesn't actively check to confirm that SQL Server components are up and running - rather it listens to errors and uses a timeout mechanism. Per BOL, disk failures are unlikely to be detected.