I've been working with a machine for a while trying to get
backups working.  After upgrading it to 4.0_BETA, I'm having
a lot of problems with doing backups to ahc or ahd scsi card
connected tape drives.

http://gendalia.public.iastate.edu/blackhole.ahd.txt is the
dmesg for the ahd cards.  Once it comes up, I seem to only
be able to write to the tapes at about 1-2MB/s.

http://gendalia.public.iastate.edu/blackhole1.txt is the
dmesg for the ahc cards.  This will write to the tapes at
up to 50MB/s, but will eventually get time outs, and at
that point, I have to reboot because the processes writing
to the tape drives are hung.  PR 21335 has some discussion
of this problem.

Upgrading to 4.0_BETA doesn't seem to have affected the
problems I was having, but it was only previously running
3.99.x, where x was 7 or 9.

Today I'm going to try it with just the mpt controller
in, and everything chained off of that.  This card fails
to see the drives connected to it every so often, and
reboots until it does are necessary, but it's better than
anything else I've tried so far.

-Tracy