I'll be upgrading clusters servers from OES1 SP2 to OES SP2a.

This will be a rolling upgrade.

Do I do cluster leave and delete server from cluster?

This seems to be a permanent removal, but maybe it sounds worse than it is.

Can anyone point me to a TID or cool solution?

I also have a need to remove one of the servers and create a space in cluster rack where other servers could be rolled to.

I plan on migrating a file services only cluster server to a server outside of the cluster for holding. Would I also do cluster leave and then delete node from cluster. I plan on migrating this cluster server which is an OES1 SP2 server to OES2 SP1b. Then when other cluster servers are upgraded, migrate this server back to OES2 SP2a.