Quote Originally Posted by warper2 View Post
I guess the big question I have is it possible to have the 2 new servers installed in the HA cluster with SP4 and
leave the other servers at sp2. When everything is done being configure remove the SP2 servers from the HA
cluster and just have 2 servers running the cluster. I am not sure whether this is a clean way to do it.
Abandon that hope. I have tried to simulate SP2 to SP4 upgrade (each node to become SP4 and joined in the cluster for smooth fail over), but from 3 nodes - 1 never managed to connect to the cluster until all nodes got SP4.
Most probably you can do it this way - new nodes in SP3 (got no issues during my tests), then migrate the resources and upgrade the other nodes to SP4.

One SP difference is possible, 2 showed in my tests that it is a problem (33 % of the cases)

Of course , you can consider SLES 15.1 if the app allows it.