On Wed, 28 Nov 2007, Peter Bauer wrote:
PERC4E/DI DC ULTRA320 SCSI RAID, 256MB Its Debian sarge with kernel 2.4.26.050719-686 #1 SMP.
OK, so I'd expect you're using the megaraid2 driver. That and kernel 2.4.26 are a few years behind current at this point, and there have been plenty of performance improvements in Linux and that driver since then. Since you're asking about this before it's a serious problem and don't need an immediate fix, you may want to consider whether upgrading to a more modern 2.6 kernel is in your future; that change alone may resolve some of the possibly too high load you're having. I doubt any 2.4 kernel is really getting the best from your fairly modern server hardsare.
Also, the PERC4E and similar Megaraid cards are known to be generally sluggish on write throughput compared with some of the competing products out there. I don't know that I'd replace it though, as spending the same amount of money adding disks would probably be more useful.
There's actually a way to combine these two ideas and get an upgrade transition plan. Buy a second disk, find a downtime window, install a newer Linux onto it and test. If that works well switch to it. If it doesn't you still have the original unmodified system around and you can at least split the disk load between the two drives.
vmstat and iostat were running with 1 second intervals.
Good, that means the responses you've already gotten made the right assumptions. There's some additional fun statistics you can collect with the Linux iostat, but sadly that needs a newer kernel as well.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org/
