We're about to move from a single server Zimbra installation to multiple servers (2 MTA/LDAP, 2 Mailbox) and want to know what's necessary when it comes to upgrade time.
1) Is is necessary for all Zimbra nodes to be running the same version? Obviously this is the way it should be, but can I upgrade one, then the next, then...?
2) Since only two of the machines hold the LDAP repository, do they have to be done first/last/simultaneously?
It seems to me I've missed an obvious piece of documentation somewhere, but I can't find it. Any help much appreciated.