qmail-ldap and GFS

Hi,

Currently, my domains and users are distributed to different mailhosts in my
qmail ldap cluster.
In this setup, If I one of the mailhost is down, the users can't access to
mailbox on this server.
To setup a redundant system,  I would like to keep mailbox on GFS file
system with multiple backends.
All backends will share the same GFS partition. There will be one mailhost
entry in openldap entries and
load balancer to distrube pop3/imap and smtp connections to backends. If one
of the backend is down, this will not effect
the users.

But, I have some doubts about locks and I/O issues. Can you please share
your experience about this kind of setup?

Thanks