Does Microsoft support running SQL Server Always On clusters for a short period of time on different CU and/or SP levels. For a week or a couple of days?

  • why do you need to hold the CU/SP patch for weeks or days?
    – user37701
    Jan 5 '18 at 4:56
  • need to ensure the application is tested with the new CU/SP - it could take some time. is there any article of this specified by Microsoft?
    – James C
    Jan 5 '18 at 5:27
  • 3
    why not do it in test environment first?? apply the patch in test before doing it prod. so you dont have to wait for the other node to be patch. it's a risky not to patch the other node because the binary is different already. when you failover to the unpatch server you dont know if your SQL Server instance will start or not. you can try that on your test environment.
    – user37701
    Jan 5 '18 at 6:12

Does Microsoft support running SQL Always On clusters for a short period of time on different CU and/or SP levels. for a week or a couple of days?

This is not an official statement but I got this from my MS friend.

It would be supported subject to condition both CU and SP are supported. But the risk and burden lies on you. I have worked with such environment for very short period, to be precise for 4 days and after that I made sure all the replicas are on same SP/CU level. If you really need it, I would suggest to try to limit this to couple of days to be on the safer side.

The correct approach would be to first test the SP/CU on UAT and then if you are happy proceed on production. But sometimes due to constraints this may not be possible. If replicas are on different SP/CU failover may cause primary replica to be on node which is not at latest SP/CU and you may see issues which was fixed in recently released SP/CU so this is very risky. The solution here is to keep such environment as short as possible.

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