SQL Server 2014 Failover cluster - Nodes on different patch levels As part of trouble shooting a performance issue with a SQL Server cluster I found out that the nodes haven't been patched properly to the same level. It is a 2 node active / passive cluster. SQL Server performance was  much better on node with higher patch level. 

The nodes have been patched to the same level now.

Just trying to understand how SQL Server and the would have  behaved in this sort of a scenario?
Would this patch level miss match have caused other issue with the cluster?
SQL Server versions on nodes were different and SQL Server needed to do upgrade or downgrade after failover. This increased failover time.