I recently asked:
From: "Leonardo C. Topa" <leo@ai.mit.edu>
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
summarize.
I received only the following reply:
From: bb@math.ufl.edu
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!
-Leonardo
This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:06:20 CDT