This morning I successfully set up a clustered, high availability pair of Zimbra (VMware virtual) servers, synced with DRBD and using Heartbeat to failover to the secondary standby server.

This is a howto that tries to cover *all* the steps, as there seems to be a great series of Howto's on the subject that in one way or another, leave something out with 'I am assuming you already (insert service here) working and will not cover this' clauses. In particular I ran into a few small hurdles with DRBD and hostnames and whatnot, so tried to document what I needed to do to make it work.