FreeBSD 5.3 freezes under heavy hdd load

[James Seward]

I'm encountering a similar problem where my desktop system will freeze
up and I'm wondering if something to do with the disks is the problem.
I have two Maxtor Diamondmax 160 SATA drives on the same SATA PCI
card, one of which is the home to FreeBSD 5.3 and the other is NTFS
from my Windows XP install (which I'm migrating away from, hooray).

The system hasn't frozen while I've been sat at it, only while it's
been left to itself. Sometimes it's doing stuff (once was extracting
Firefox for a portupgrade), sometimes it's not (being left overnight
doing nothing in particular). Either way it freezes and has to be
reset.

While rebooting, it often complains about /usr to the extent that it
wants me to manually fsck it before the boot will complete. It's
always /usr.

What makes the disk the suspect is log messages saying there's a
timeout on the disk and it has two more retries, from which the
machine usually continues. Unfortunately because of the freezing I
can't see if that's happening when it dies.

I would post some actual log messages but I had to leave it dead this
morning due to lack of time to bring it up :) Tonight I'll check it's
not overheating but I don't think that's the case - this machine
doesn't usually run hot.