What is the catch or the caveats apart from the few minutes of downtime for the Outlook user if I do the patching for the following clustered Exchange Server box:
Unicast NLB cluster Hub Transport
Start with the Node 1 and then followed by Node 2
Cluster Continuous Replication Mailbox Server
Start with the ACTIVE Node 1 so that after the patching the MBX role is fail over to PASSIVE Node 2
and then the current ACTIVE Node 2 patched to bring the MBX role failed over to PASSIVE Node 1
I know that it is rather weird or unorthodox way to patch it but I try to avoid manually patching the Exchange Server and minimize the amount of downtime (twice if I start the patching from the passive node to active node).