Lockups with dump(8)

I can nearly reliably crash
  5.1-BETA #2: Fri May  9 19:46:44 CEST 2003
when using dump(8) like this:

# dump -0aun -L -f - /usr | gzip2 | \
>    ssh -c blowfish voyager_at_dumphost.domain.tld \
>        dd of=/dumps/voyager/usr-fs.l0.gz

Somewhere between 10% and 80% of the dump,
this message pops up:

  ad0: READ command timeout tag=0 serv=0 - resetting
  ata0: resetting devices ..

and the system locks up. I cannot switch consoles,
but can still ping the box from the outside.

This doesn't happen on smaller filesystems like
/ or /var, only with /usr (and here only in
approx. 95% of cases).

It does happen in multiuser _and_ singleuser
mode. I've fsck -f all filesystems before.

There is only one disk on ata0, nothing more.

I've swapped drives, controllers and motherboards.
Same problem on all machines.

-Farid.

-- 
Farid Hajji -- Unix Systems and Network Management.
http://www.farid-hajji.net/address.html
Quoth the Raven, "Nevermore." --Edgar Allan Poe.