[exim] Choosing an I/O Scheduler on Linux

I have been having a somewhat bad time with overloaded I/O on a CentOS
4.x server running Exim, Dovecot and spam/antivirus. I switched from
default CFQ for a scheduler too DEADLINE and things improved quite a
lot. I was just wandering if maybe using AS would be better yet on an
email server?

http://en.wikipedia.org/wiki/Anticipatory_scheduling

So what is everybody using here? Doing any tuning to the schedulers?

Matt