SUMMARY: help with bad DAT tape

From: Leonardo C. Topa (
Date: Thu Jul 25 1991 - 14:24:37 CDT

I recently asked:

   From: "Leonardo C. Topa" <>
   Date: Fri, 19 Jul 91 17:36:27 EDT
   Subject: help with bad DAT tape
   Hello everybody,
   I think I really did it this time, but before giving up I thought I
   might ask you netters if there is any remote possibility of recovering
   data off a "bad" tape.
   Here is my problem: I have a DAT tape drive (Archive-Maynard model
   4330) attached to a sparcstation running Sunos 4.1.1 and I have *one*
   copy only of some files on a tape in dump format. This morning, while
   I was trying to retrieve some of these files interactively (restore -i),
   I got a message "Read error while restoring <filename>" and the
   following message was logged to the console:
   st1: Error for command 'read', Error Level: 'Fatal'
           Block: 226296 File Number: 1
           Sense Key: Media Error
   Now, I don't care to retrieve that particular file, but it turns out
   that the files I want are past that point on the tape. So the question
   is: is there any way I can convince the tape drive to skip over the
   bad record without aborting everything? I tried to read the tape with
   dd (dd if=/dev/rst1 bs=61440 of=tape.dump) and I tried to use mt to
   skip over the bad record (mt -f /dev/rst1 fsr 1884) but both methods
   produced an I/O error.
   Am I really out of luck? Thanks for all your answers and I will

I received only the following reply:

   Date: Mon, 22 Jul 91 19:54:55 EDT

> I tried to read the tape with dd (dd if=/dev/rst1 bs=61440
> of=tape.dump)

   % man dd
        conv=ascii Convert EBCDIC to ASCII.
       ----> noerror Do not stop processing on an error.

   Hope it helps.

I tried this, but the problem seems to be at much lower level: after
some experimenting, I now think that the DAT tape drive senses the bad
record and decides to abort everything and it even rewinds the tape. I
double checked this theory by trying to skip over to the end of the
dump file with "mt -f /dev/nrst1 fsf 1" but that fails too as soon as
the bad record is encountered.

The unit works perfectly with other tapes and they all have been
written within a short time span (a few months) so I strongly doubt it
has to do with head misalignment over time. Cleaning the heads didn't
help either. Those files I needed are gone.... sigh!


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