[Dovecot] Redundant shared mail store?

[Leroy van Logchem]

 > We are planning on having a backup/spare server and doign RSYNCS to 
it, but that may not be acceptable if you don't the possibility of 
loosing any mail.

We are using drbd and it works very well. Combined with Heartbeat and 
some APC powerswitches it's foolproof at fail-overs.
Use a direct gigabit link between the servers using 9000 frames bytes 
proves to be enough to keep everything 100% in-sync.
The additional mbox'es are placed in the users home directories, also 
high available NFSv3 servers using drbd. We have
more then 20TB realtime syncronized using drbd 0.7.22; so far never lost 
a single bit. Use the seperate partition for meta-
data so you can mount a 'none-drbdified' partition at anytime if 
troubles would emerge (never had to use it but better to be
safe then sorry).

Our golden combination consists off:
Beefy hardware with Areca 1260 raid controllers
RedHat enterprise 4U4
Drbd 0.7.22
Heartbeat 1.2.4
bunch of scripts for the fail-over to control the power switches
( down means really go down using the stonith feature )

Goodluck,
Leroy