For redundancy, I was thinking of creating the IMAP folder dir and spool dir on the SAN and then having two mailservers setup identically using cyrus. If the primary server goes down for any reason, the secondary would automatically begin receiving/delivering mail based on the MX records in DNS.
Please bear in mind, that the MX priority in DNS is not honored by all mailsystems, so it could happen that your secondary server has traffic while your first server also has traffic, possibly delivering to the same mailbox at the same time.
Gr,
Nils.
--
Simple guidelines to happiness:
Work like you don't need the money,
love like your heart has never been broken and dance like no one can see you.