On Fri, 2008-03-14 at 21:19 -0700, Marc Perkel wrote: > What stat tools specifically? Yes, I think I'm IO bound. I think it's > the number of connections and the TCP stack that's slowing me down.
You have a single SATA II drive. They (mostly) don't support TCQ (Tagged Command Queueing) so access to them is effectively sequential; this makes them very inefficient (and slow) for truly random accesses. More modern drives SATA do support TCQ but a lot of controllers don't; both devices need to in order to make use of it. For the uninitiated, TCQ allows a drive to re-order the waiting commands according to head position, platter rotation and seek distance/time to get the best usage of the disk. Without TCQ, commands are processed sequentially. In your case, your accesses under load will be something like this: Reading - hints databases, lookup databases, queue files, binaries, config files Writing - hints databases, queue files, log files With many thousands of connections this will all be taking place at the same time, causing the heads on the drive to ping around at a huge rate. Your system is simply waiting for the disk to catch up. SATA - even SATA II - is not, in my opinion, usable for high R/W situations. You can improve it using a decent RAID controller and multiple disks, but you might aswell invest in the largest number of high-end SCSI, SAS (or even FC disks, depending on chassis) and put them together in the most performant array you can build. That depends on circumstance. None of this is really related to Exim. It's Hardware 101 :) Graeme -- ## List details at http://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
