Someone asked me a question about the use of a CAS array when you do not have a load balancer but do have two CAS nodes.
In fact, they are actually in a migration scenario where there is currently one old CAS, and will be two (old and new), and then at the very end, one (new).
I asked them a question: can you move mailboxes from one to the other quickly?
If so, they could just adjust the DNS record so "CASARRAY1" now points at the new CAS.
Of course, adjusting the TTL would be a good idea so clients do not retain the old outdated record in their cache too long.
But what if the two CAS coexist for a couple weeks?
This is where I am not so sure.
We could either create another DNS record to link CASARRAY1 -> IP of new CAS (this would result in round-robin).
or... simply leave it pointed at the old CAS.
Old CAS should connect clients migrated to new CAS (which is also new MB server) to their mailbox.
Then adjust DNS record as mentioned above when it's time to retire old CAS?
Which is the better option?
Please mark as helpful if you find my contribution useful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you.