SUMMARY: tape drive craziness

From: John Valdes (
Date: Wed Oct 24 1990 - 14:33:14 CDT

(Sorry for the delay in posting this. I mail it earlier, but apparently it
didn't go through.)

Hello all,

Last week I reported having problems with a 1/4" Archive tape drive which
thought it was an Emulex MT-02:


We have a 1/4" Archive tape drive on a 4/330 (OS 4.1). A user was tar-ing some
files to it and sending different mt commands to it. Apparently, something
went wrong, because now the drive thinks its an Emulex MT-02! Since the Emulex
uses QIC-24, we can't read any of our QIC-150 tapes, and all attempts to write
to the drive produce errors. My guess is that somehow some command was sent to
the drive which switched it to Emulex mode(?). If so, is there some way of
switching it back? I couldn't find any obvious ioctl's which could do this.
Or must the drive be power cycled? How can a user reset the operating mode of
a tape drive? Is this a bug in the st driver? Or is our tape drive going bad?


I received a response from one person (MaryBeth Gallacchi) who had a similar
problem with an Exabyte, and another (Kurt Schreiner) who had the reverse, a
QIC-24 which thought it was a QIC-150. Unfortunately, no one had an answer
on how to switch it back, so I rebooted the machine (not power cycled), and
this cleared the problem.

The similar problems people reported with different tape drives, plus the fact
that nothing could be written to tape with the drive when it appeared to be in
QIC-24 mode (although it was able to erase) leads me to suspect that the SCSI
interface for the drive was at fault and not the drive itself. I don't think
that the drive was emulating an Emulex MT-02. Apparently, mt uses the
MT_TAPE_INFO table in sys/mtio.h to match up drive type numbers returned by the
drive to a string describing the drive. My guess is that the SCSI interface
for the drive was in a bad state and was just returning the number for the
Emulex when polled for the drive status. (I thought the drive actually
returned a string describing itself--silly me!)

Thanks to those who responded:

Don Lewis <>
Stefan Mochnacki <>
MaryBeth Gallacchi <>
Joe Pruett <tessi!joey@nosun.West.Sun.COM>
Kurt Schreiner <>

Sorry to disappoint anyone with hopes of writing QIC-24 tapes with a QIC-150

John Valdes

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