SCSI Tape drive question

[bscott at ntisys.com]

On Thu, 17 Jun 2004, at 7:19am, colet at code-energy.com wrote:
> I've set up a SCSI tape drive on a system.  The drive is a SONY AIT
> *mumble mumble* on a symbios based card. 

  Oh, that's easy.  The answer is mumble mumble.

  Seriously, to help, we need information.  We're not psychic.  Model of
tape drive.  Model or chipset of SCSI host adapter (or at least the name of
the Linux driver).  Linux distribution and release.  Kernel version.  Come
on Cole, you know we need this.  :-)

  The contents of the "files" in the /proc/scsi/ directory branch are likely
to be of use in determine some of this information.

> I have to reboot the system to get rid of the mt process, and then power
> cycle the tape drive to make it work again.  If I don't power cycle the
> tape drive, all mt commands will just hang and not even respond to a kill
> -9.

  If you look as "ps aux", I'm sure you'll see the "mt" process has status
of 'D', which is short for "uninterruptible sleep".  That means the process
is sleeping on a kernel system call.  You can send the SIGKILL signal, but
the process will not receive it until the kernel call completes and the
process wakes up again.  The kernel system call in question is doubtless a
call to the SCSI device layer.

  The question is, what is the SCSI driver doing?  Have you checked syslog
and dmesg for any messages?

> By "locks up", I mean that the current mt command (seemingly always
> "erase") runs forever.

  The "erase" command typically takes a really long time to complete.  That
might indicate a problem with SCSI device disconnection.  That is when the
initiator sends a command to the target, and then the target "disconnects"
from the SCSI bus while the command completes.  This frees the SCSI bus for
other operations.  If I knew anything about your equipment, I might be able
to give further insight, but since all I know is that you have a tape drive,
I can only speak in generalities.

  BTW, why are you running erase, anyway?  It's typically not needed for
modern tape technologies (such as AIT).

> Any thoughts?

  Aside from giving us the vital information already requested: I would
recommend checking firmware revisions on the tape drive, host adapter, and
mainboard.  See if updates are available, and if so, install them.

-- 
Ben Scott <bscott at ntisys.com>
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