failover scenario's for replication

[Paul Dekkers]

Hi,

I was wondering what people consider best practice as failover scenario
in a replication enviroment.

Right now, it looks tricky to me to enable replication after failover,
or the replicated machine itself if you're not sure that the replica is
identical and the sync-processes finished completely: if a message-file
is in place on machine A (say "7.") but it was not replicated to machine
B while that one becomes the master, the machine B will create a new
file 7. and both machines consider this file synchronised after that:
also if roles switch back, you have two different (with one isolated)
copies of 7.
(Probably a thorough check is needed to ensure the consistency 'once
again' and copy files from one side to the other... so I hope that's
where best practice comes in ;-))
Or is it only preferred to use a replica if there is a really serious
crash on the (previous) master?

It sounds nice to me if I could use heartbeat or (u)carp (/ifstated)
like systems to start and stop a sync_client or sync_server copy of
cyrus (both different cyrus.conf) as soon as the state of the virtual
interface changes, but then it is even more likely that some replication
process is not finished without an admin even noticing it.

Curious,
Paul