SQL version, edition, SP level variance across SQL cluster nodes

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SQL version, edition, SP level variance across SQL cluster nodes

webrunner

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Points: 31866
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August 23, 2018 at 3:06 pm

#415500

Hello experts,
As an accidental DBA, I had naively believed that in a SQL cluster, everything related to the SQL instance would necessarily be identical (or would need to be identical as a result of the cluster creation) across nodes. Recently, however, someone asked if both of our nodes (active-passive cluster) had the same version because of some patching issues.
Could someone educate me on what can and cannot vary from node to node in a SQL cluster instance? In our case we are running on-premise SQL 2016 EE VMs but with some databases still in SQL 2012 compatibility level.
From the bit of research I've done so far, it seems like the following is true:
1. SQL editions have to be the same for both nodes in an active-passive cluster - that is, you can't have Node A running Standard Edition and Node B running Enterprise Edition.
2. SQL SP levels can be different for both nodes since each node has its own SQL binaries.
3. SQL versions (2012, 2016, 2017) -- ?? -- this one I don't know at all.
Thanks for any help on this - including whether there's some MS documentation that already spells this out. As usual, clusters throw me another curveball lol.
- webrunner
-------------------
A SQL query walks into a bar and sees two tables. He walks up to them and asks, "Can I join you?"
Ref.: http://tkyte.blogspot.com/2009/02/sql-joke.html

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Steve Jones - SSC Editor SSC Guru Points: 736280 More actions · Answer 1

Since clusters can be used to upgrade, I think you can certainly patch one side to a new sp/cu and it will continue to work. You can also upgrade some editions of SQL Server as well

https://docs.microsoft.com/en-us/sql/sql-server/failover-clusters/windows/upgrade-a-sql-server-failover-cluster-instance-setup?view=sql-server-2017

The problem here is that if certain things change, you can't fail back to the previous version. This is sometimes the case with SPs, so the recommendation is that when you patch one node, you patch the other in short order.

Steve Jones - SSC Editor SSC Guru Points: 736280 More actions · Answer 2

There's also this: https://docs.microsoft.com/en-us/sql/sql-server/failover-clusters/windows/upgrade-sql-server-failover-cluster-instance-2008-2012?view=sql-server-2017

webrunner SSC-Dedicated Points: 31866 More actions · Answer 3

Thanks so much, Steve!!

I'll review that information.

- webrunner

-------------------
A SQL query walks into a bar and sees two tables. He walks up to them and asks, "Can I join you?"
Ref.: http://tkyte.blogspot.com/2009/02/sql-joke.html