Exchange 2010 upgrade (SP2)
I'm going to be upgrading my exchange infrastructure from 2010 RU5 to 2010 SP2 (missing SP1). I've chosen SP2 because SP3 hasn't been out long enough yet for my liking. I currently have one CAS and three mailbox servers. It's the first time I've performed an exchange upgrade.
How long does it take each server to upgrade? Are there any caveats that I should be aware of? Can I upgrade my CAS first, and leave it running for a few days in coexistence with the not yet upgraded mailbox servers?