I've successfully configured heartbeat 2.1.2 and DRBD on CentOS5 with Zimbra 5.0RC2.
I'm down to one last quirk that I don't quite understand. If I issue a reboot or shutdown command to the active server, heartbeat tries to stop the services. All of a sudden, zimbramon starts firing up the services again and it takes the box longer to shutdown (by about a minute).
Does anyone have any insight into this?