Cluster with different versions- 2016 and 2014

  • It's a bit unusual case, I know. We have sql server 2016 cluster (2 nodes, windows 2012) with 2 instances running (i.e. Act/Act). Request is to add one more instance but 2014 (same edition- Ent). Why? It's for chat component that Vendor tested only for sql server 2014 (i.e. 2016 is not supported). Certainly new dedicated VM will be better but as always... money (hardware + license).  
    Anyhow have couple questions:
    1) Can we do this,  i.e. combine 2014 and 2016 instances on the same cluster?
    2) should we do this, i.e. where is the catch?
    Let's say cluster has enough resources to support 3 instances- what else we should keep in mind?
    Thanks in advance.

  • Hi,

    The first problem you will bump into is that is impossible to restore backup of 2016 on an earlier version of SQL Server.
    The only way to have replicas with different versions is during the Rolling Upgrade process - https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/upgrading-always-on-availability-group-replica-instances

    So the answer for your question - it is impossible.

  • Probably I was not clear- I am not going to restore any backup from 2016 to 2014. Question is about creating cluster with instances with different versions, i.e. adding to existing 2016 instance new one- 2014 as same cluster resource. There was post while ago on SSC regarding 2005/2008 combination on the same cluster and answer was- it's possible. I just wondering if it's still true for 2016/2014 instances? Unfortunately cannot find any MS docs on that matter.

  • Yuri55 - Thursday, December 21, 2017 5:34 PM

    Probably I was not clear- I am not going to restore any backup from 2016 to 2014. Question is about creating cluster with instances with different versions, i.e. adding to existing 2016 instance new one- 2014 as same cluster resource. There was post while ago on SSC regarding 2005/2008 combination on the same cluster and answer was- it's possible. I just wondering if it's still true for 2016/2014 instances? Unfortunately cannot find any MS docs on that matter.

    So, you are adding a third node that will have instances of both 2016 and 2014.  The existing nodes will also have 2016 and 2014 as well.  If that is the case, I do believe that would work as long as you have the same versions of SQL Server supporting each other.

  • Thanks Lynn, this is the plan- add 3-rd node to cluster, install 2016/2014 version on all 3 nodes (first 2 nodes certainly have already 2016 running) and make 3-nd node default for 2014 instance.
    Any pitfalls we should be aware of, any supporting docs from MS? Really appreciate your comments.

  • Yuri55 - Thursday, December 21, 2017 5:53 PM

    Thanks Lynn, this is the plan- add 3-rd node to cluster, install 2016/2014 version on all 3 nodes (first 2 nodes certainly have already 2016 running) and make 3-nd node default for 2014 instance.
    Any pitfalls we should be aware of, any supporting docs from MS? Really appreciate your comments.

    On second thought- seems 3 nodes cluster won't work for us as installing new instance on extra node will certainly require extra license for sql server 2014. Therefore to rephrase my question- 
    can we  add sql server 2014 instance to 2 nodes cluster with 2 sql server 2016 instances already running there? Thanks

  • Yuri55 - Friday, December 22, 2017 9:31 AM

    Yuri55 - Thursday, December 21, 2017 5:53 PM

    Thanks Lynn, this is the plan- add 3-rd node to cluster, install 2016/2014 version on all 3 nodes (first 2 nodes certainly have already 2016 running) and make 3-nd node default for 2014 instance.
    Any pitfalls we should be aware of, any supporting docs from MS? Really appreciate your comments.

    On second thought- seems 3 nodes cluster won't work for us as installing new instance on extra node will certainly require extra license for sql server 2014. Therefore to rephrase my question- 
    can we  add sql server 2014 instance to 2 nodes cluster with 2 sql server 2016 instances already running there? Thanks

    If you are adding a SQL Server 2014 instance to both nodes and they are supporting each other than yes.

  • OK,
    will give it a try
    Thanks

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