[plug] Tape device goes missing

[Ryan]

Hi PLUG,

I posted about this a while back, but this time I have not rebooted and
can test your wonderful ideas ;)

I was writing stuff to tape (HP DAT 40i DDS-4) in blocks:

	tar cvvf /dev/tape /blah/blah  (repeated lots)

I was then playing around seeking to specified blocks and listing
contents:

mt asf 5; tar tvvf /dev/tape

All good, then I wanted to add more data so I tried:

	mt eod

Once that completed  /dev/tape (nst0) is 'missing'

Every command I try on the drive reports:

	/dev/tape: No such device or address

If i specify the device name:

	# mt -f /dev/nst0 status
	/dev/nst0: No such device or address

Here is some info:

# ls -l /dev/nst0 /dev/tape
crw-rw----    1 root     tape       9, 128 Jun 13  2001 /dev/nst0
lrwxrwxrwx    1 root     root            4 Nov  7 13:08 /dev/tape ->
nst0

dmesg:
(ips0) Reset Request - Flushed Cache
scsi: device set offline - command error recover failed: host 1 channel
1 id 11 lun 0
Device not ready.  Make sure there is a disc in the drive.

If I only do straight single writes to the tape it never stuffs up, it
is only when I play around going forward and back that it seems to die.

If I reboot the machine, the drive appears fine, all the data is on the
tape and I can continue on as usual until it muffs up again.  As it
stands now, the tape light is on - i can eject and reinsert etc and
other devices on the same SCSI bus are humming along happily.

Not having any other tape drives to compare it too, do I possibly have a
dodgy drive, or am I using the commands incorrectly?

Is there anything I can do to test for the presence of the drive on a
lower level than mt etc?

Any other ideas about what is going on?

Thanks,

Ryan