Post reply

AG across different SQL versions?

  • August 7, 2017 at 2:13 pm

    #324840

    Can one create an AG with nodes of different SQL versions?  For example, a three node AG with one node at SQL 2012, the second node at SQL 2014, and the third node at SQL 2016?

  • August 7, 2017 at 6:18 pm

    #1954400

    Yes...sort of. Assuming you start out with the databases on the 2012 instance, and set it as primary, you can restore the database(s) to the 2014 and 2016 instances and join the database(s) to the AG. The problem could crop up if/when either the 2014/2016 instance becomes primary, and for whatever reason, the database(s) have to be dropped on the lower version instance--you cannot restore a database from a 2016 instance to a lower version (either 2014 or 2012). So, while the answer is "yes", there is risk involved. If everything remains up and running, there wouldn't be a problem...but that's the whole reason for AlwaysOn...to be able to recover when something goes wrong. Therefore, for best practice, it would be best to have all instances participating in AlwaysOn be the same version.

    Alan H
    MCSE - Data Management and Analytics
    Senior SQL Server DBA
    Best way to ask a question: http://www.sqlservercentral.com/articles/Best+Practices/61537/

  • August 9, 2017 at 5:27 am

    #1954583

    SQL_Hacker - Monday, August 7, 2017 6:18 PM

    The problem could crop up if/when either the 2014/2016 instance becomes primary, and for whatever reason, the database(s) have to be dropped on the lower version instance--you cannot restore a database from a 2016 instance to a lower version (either 2014 or 2012). So, while the answer is "yes", there is risk involved. If everything remains up and running, there wouldn't be a problem...but that's the whole reason for AlwaysOn...to be able to recover when something goes wrong. Therefore, for best practice, it would be best to have all instances participating in AlwaysOn be the same version.

    The problem will crop up if you attempt to set the secondarys to read only, they'll need to be left in the restoring state.
    This scenario is only really useful and in fact designed to support rolling upgrades

    -----------------------------------------------------------------------------------------------------------

    "Ya can't make an omelette without breaking just a few eggs" 😉

Viewing 3 posts - 1 through 2 (of 2 total)

You must be logged in to reply to this topic. Login to reply