[exim] exim using intensive hdd access

Hi,

I'm currently having a issue when receiving approx 600+ SMTP sessions
concurrently (at least thats how many exim -MC commands are running).
I'm running it on a HP DL380 G5 Chassis.

Current setup of the server is as follows:

2 drives (software raid1) - xfs - /
2 drives (software raid1) - ocfs2/drbd /mailfolders (however running as
a single node for now).

There is a big bottleneck when handling multiple messages here, and I'm
guessing IO.

The Idea is to make several servers setup like this and mirror the
"/mailfoders/" volume using ocfs2, and drbd. In an attempt to have
complete redundancy, so If a box had to fail the next box in line would
have all the mails and etc....

Mailboxes live in a SQL database, on this box aswell. Using courier as
the pop3a and imapa.

Any suggestions on a proper redundant setup, or is this the way but
needs some tweaks ??

Thanks,
Michale