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Date:      Wed, 1 Oct 1997 14:39:54 +0100 (BST)
From:      Mr M P Searle <csubl@csv.warwick.ac.uk>
To:        dburr@poboxes.com (Donald Burr)
Cc:        aic7xxx@freebsd.org, freebsd-scsi@freebsd.org, freebsd-hardware@freebsd.org
Subject:   Re: Odd behavior of Wangtek 5525ES SCSI tape drive under 2.2.2 and A
Message-ID:  <1996.199710011340@anise.csv.warwick.ac.uk>
In-Reply-To: <XFMail.971001031306.dburr@POBoxes.com> from Donald Burr at "Oct 1, 97 03:00:52 am"

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-- Start of PGP signed section.
> I am the proud owner of a
> 
> (ahc0:4:0): "WANGTEK 5525ES SCSI 73R1" type 1 removable SCSI 2
> st0(ahc0:4:0): Sequential-Access density code 0x0,  drive empty
> 
> Wangtek 5525ES SCSI-2 tape drive (525MB QIC-525 drive).  It's connected to
> my brand-new Adaptec AHA-2940AU PCI SCSI controller (aic7860), on my
> FreeBSD 2.2.2-RELEASE system.
> 
> This setup works pretty well.  I've already done several successful dumps
> to this device, and have created more tar tapes than I can shake a stick
> at.
> 
> The weirdness comes with the `mt' command.  Basically, any "mt" command
> that causes the tape drive to spin (weof, retension, fsf, etc.) SOMETIMES
> (probably 1 in 10 times) causes the system to "soft hang".  Processes keep
> running, I can switch to another VC and login, or telnet to the machine
> over the network, etc.  BUT the mt process is hung -- I can't exit with
> Ctrl-C, or kill (even kill -KILL) it.  Ctrl-Z fails to suspend the thing,
> and the process fails to die on a reboot/shutdown (this results in the
> "syncing disks...giving up" message).  And the tape drive don't spin.
> 
> BUT, other commands that access the tape drive (tar, dump, even dd) work
> fine!!!
> 
> unix% tar cv /some/dir
> /some/dir/a
> /some/dir/a/file
> /some/dir/b/dir
> /some/dir/c/file2
> ...tape drive chugs away, and finishes successfully
> unix% dump 0auf /dev/rst0 /
> DUMP: ....
> [successful dump]
> unix% dd if=/dev/rst0 of=/dev/zero
> ...blahblahblah
> unix% mt retension
> [ oops - hung.  Big Red Button time. ]
> 
> I have tried the usual remedies -- checking cables and termination,
> disconnecting all SCSI devices EXCEPT the tape drive, etc.  Nothing helps.
> 
> As stated above, I run 2.2.2-RELEASE.  I have tried one of the RELENG
> kernels (970913 I think), with the same behavior.  Unfortunately I'm not
> man enough to try CURRENT. :)
> 
> My controller is an Adaptec AHA-2940AU PCI SCSI controller (aic7860).  The
> controller works great, and all of my other devices (JAZ, cd-rom, etc.)
> work flawlessly.
> 
> Any ideas?
>

Well, no, but you're not the only one. I've got a Tandberg 250MB QIC-250 drive,
on an NCR controller. 'mt fsf' will often cause SCSI errors on all devices,
a SCSI reset, or a completely hung system (not just that process).
'cat /dev/nrst0 > /dev/null' has no problems, even though it is doing the same
thing. I'm not sure that my problem is the same as yours (this drive is generally
dodgy - hangs and SCSI errors also happen if I don't wait for one command to 
complete before running another, or if I try to read two files without rewinding
and moving back again between them...), but it looks similar. Anyway, I've
worked round it by replacing all the mt commands (mostly fsf) with things like
the 'cat /dev/nrst0 > /dev/null' to move forward a file, and anything with /dev/rst0
to rewind. You could probably do the same for a lot of the other mt commands as well.
You could also try the 'wait for tape to stop clunking before next command' fix
in case mine isn't the only drive in the world to do this. (or put big sleeps in
scripts) This is with 2.1.0, so it may be the same thing despite the different
errors.



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