Had some trouble with Debian in VMware Server 2.0: I/O was horribly slow, 100% IOwait when doing the simplest things, hdparm showing 11MB/s throughput.
This was fixed by shutting down the VM, changing the SCSI adapter from Buslogic to LSI logic and booting up again. hdparm is at 63MB/s now. The machine, which will be an SMTP mail exchanger, now scans 8 mails per second (Postfix before-queue filter via amavisd-new+ClamAV) in 10 concurrent sessions. Not bad at all.
Debian is by far the simplest choice for an SMTP content filter because it’s not neccessary to bring in any dependencies by hand. Cool.