[Linux-HA] active/passive and SAN

[FG]

Hi all,

I need some advices about my configuration for 
high-availability.
I would like to set up an active/passive 
configuration for our POP/IMAP
server.

We have two servers with each one two HBA cards 
(FC) attached to a SAN
IBM DS4000 where we store the mailbox.

My concern:
In case of a failure,  i'm worry about  corruption 
data  if the  backup
server attempts  to mount the mailstore (located 
on the san)  whereas
the first one is not really dead or if the first 
one doesn't umount the
mailstore on the SAN  (for example  in a case of 
network failure).

I read, of course, we can use STONITH to ensure 
the first would be dead.
For my configuration, do i really need this ?
Or perhaps somebody knows that a  SAN DS4000 can 
give access to the
logical drive for the second server and block the 
access to the first one ?

If someone have experience with heartbeat and IBM 
SAN in an
active/passive configuration, i'm interested...

Thanks a lot
Best regards