High load average on Ubuntu 7.10/8.04

[Andrew Carter]

I've been dealing with a problem with my Dell Precision 490 for some
time now. I've been using this machine since late last year at work. The
problem is that the load average goes through the roof (around 10) when
the disk is is used heavily. For example, tar xvzf on a 4GB tarball
brings the machine to its knees.

I originally was running Ubuntu 7.10 64-bit. I recently did a clean
upgrade to Ubuntu 8.04 64-bit. I've tried turning off all the compiz
effects, killing as many other processes as I can but it always kills
the machine when the disk is heavily accessed.

I'm not exactly sure how to diagnose this problem. I'm thinking it could
be a kernel problem, a driver problem for the SATA disk, or a firmware
issuee. I believe I have the newest Dell BIOS. I'm not sure about the
whole kernel thing since I don't see widespread talke about it. And my
newer OptiPlex at home hasn't shown any issues (and I mess with lots of
large video and audio on it).

Specs:
Dell Precision 490
BIOS A07
4GB RAM
Intel Xeon 1.6GHz (2 dual cores)
Ubuntu 8.04
Kernel Linux 2.6.24-17-generic
250GB WD SATA hard drive

Thanks,
Andrew