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Date:      Wed, 20 Dec 2006 10:59:54 -0600
From:      Derek Ragona <derek@computinginnovations.com>
To:        Mark Kane <mark@mkproductions.org>, Dan Nelson <dnelson@allantgroup.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: SCSI Tape Drive Problems
Message-ID:  <6.0.0.22.2.20061220105616.0251a770@mail.computinginnovations.com>
In-Reply-To: <20061220020947.135537e1@localhost>
References:  <20061219221610.4bcdb4c4@localhost> <20061220051644.GB41207@dan.emsphone.com> <20061220020947.135537e1@localhost>

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You can get "ringing" on a SCSI device from bad or loose cabling which will 
generate a lot of SCSI errors.  There are limits to cable lengths and you 
need to be sure you use proper cables for every device (and rated for the 
SCSI bus speed.)

You will do best to pull out any un-necessary hardware, use a minimal 
hardware setup.  You should also run diagnostics from the drive 
manufacturer and verify the tape and drive.  Last thing be sure to erase 
the tape before testing it.

         -Derek


At 02:09 AM 12/20/2006, Mark Kane wrote:
>On Tue, Dec 19, 2006, at 23:16:45 -0600, Dan Nelson wrote:
> > Timeouts and unexpected busfree errors like these are indicative of
> > cabling or termination problems.  I don't think DLTs auto-terminate,
> > for example, so try putting an external terminator on the 2nd plug on
> > the back of the unit (or if it's an internal drive with one plug,
> > terminate the cable the drive's plugged into).  Once you get those
> > errors sorted out, see whether you still get incorrect volume full
> > messages.
>
>Thanks very much for the replies. Both drives are external, and they
>both have terminators on the back. The setup is like this:
>
>The DDS autoloader is connected to the back of the Adaptec card via a
>new external HD68 cable and the terminator that came with the drive
>is on the second plug of the unit.
>
>The Sun DLT drive is connected via an external HD50 cable to an adaptor
>that turns it into an internal cable which is then connected to the
>Adaptec card internally. It has a Sun terminator on the second plug on
>the unit.
>
>The cable that connects the DDS autoloader is brand new. It's not a
>major brand name, but it's listed as "double shielded", "UL20276
>listed", etc. The cable that connects the DLT unit is an older Adaptec
>one (possibly used) purchased for a few dollars locally. I could
>understand if that cable was a problem for writing using that drive, but
>having the issue on both drives like this with two separate cables just
>seems like it's something else.
>
>By the way, the green LEDs on both terminators are illuminated so they
>should be working.
>
>With the DDS drive, it does not give any errors to /var/log/messages
>like the DLT drive does. cpio just quits with that "Internal overflow,
>aborting" error (which doesn't happen with the DLT). Do you guys know
>specifically what that message means? With the DLT drive, cpio actually
>gives the volume full errors but with the DDS it's only "Internal
>Overflow" and nothing else anywhere that I can see. Internet searches
>for the "Internal Overflow" message have not turned up much helpful
>information.
>
>Thanks again.
>
>-Mark
>
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