5

No. Once you fail over to the higher version, you cannot go back down. Using Distributed AGs for a mixed version topology only works when the writable main AG (specifically individual the read/write replica) is on the lower version. From the docs (bolding mine): Distributed availability groups in SQL Server 2017 or later can mix major versions of SQL Server ...


2

Instance A and B will release memory when the system is under memory pressure, but it's not instantaneous. So instance C may not be able to allocate memory when it needs to. So yes, the typical solution here is to reduce the Max Server Memory of each instance so the others always have enough to function minimally. Also you should also set LPIM on instance ...


2

If you want to mix FCI and AG, you can do so and it is supported. Below is a hypothetical configuration. Failover Cluster Instance (Node A, Node B), addressed as Server 1. All clients connect to Server 1. Only one Node is live at a time (i.e. only one node has control of the storage that has the databases on it. Node C lives in your Disaster Recovery ...


2

It's anybody's guess why the UI is preventing you from being able to use the copy-only checkbox. So I can't give you an answer and don't think it would be productive to throw out guesses. I can offer a workaround (and generally, this is a better way to accomplish just about anything a pointy-clicky UI tries to do for you): Press the Script button Copy the ...


1

On the "Cluster Quorum Information" screen, the "Vote Count" column indicates if this server is eligible to vote, not that it is currently casting it's vote. Depending on your OS version, configuration, and a few other factors, you are either seeing 50% of voters offline, and thus do not have quorum (in which case the Windows cluster &...


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