I have a 4 node cluster that has 8 instances. 7 instances are running on SQL Server 2012 and one instances is running on SQL Server 2014. Now the original plan was just to upgrade everything to 2014 but a few of the instances will be sunset in the near future and the application team is unsure how it will handle the upgrade. :crazy:
I so my problem is a few of the instances have to be upgraded from 2012 to 2014. So I want to verify I can upgrade four 2012 instances to 2014 and leave the other two on 2012. Mind you I already have 2014 installed as one instance is already running on it. So my question is when I run the SQL Server upgrade to 2014 how does it handle the already installed Sql server 2014 and will this cause any issues with the fail over cluster?