On Fri, May 01, 2009 at 04:46:29PM -0500, Len Philpot wrote:
> I have scanned in old tapes, long past both their browse and retention 
> policies and recovered data from them. However, I've never tried to scan 
> in an expired and relabeled tape. My understanding is that relabeling 
> simply rewrites the label header on the tape and doesn't overwrite nor 
> erase the entire tape (indeed, such a procedure would take three forevers 
> if that was the case).
> 
> To scan in a relabeled tape, you would of course have to first delete it 
> from the database, but would any of the data on it be discoverable by 
> Networker or would it scan in as a blank tape?

It's virtually impossible to read past the last write on a tape without
special equipment. 

If a tape has been relabeled, consumer drives won't read anything past
the newly written label, so the tape is pretty effectively erased.  I
don't think this happens with 9-track tape, but it does with
DLT/AIT/LTO.  Only thing I can think of at this point would be to send
to a recovery house that should have modified firmware drives available.

It has been suggested that you might be able to begin writing to the
tape at the end of the relabel.  The new write will overwrite the
recently added EOM.  Then during that write, power-off the drive so it
doesn't have a chance to write a new EOM.  Then try to read the tape.
I've tried it with DLT media and wasn't able to see anything.  I kept
getting "sync error"s from the drive when I'd forwarded past the recent
writes.  I can't be sure that I was doing everything correctly, but I
haven't heard of anyone else being successful with this technique.  I
haven't repeated the experiment with LTO.  (I also don't have a
standalone LTO drive that's easy to power-off independently).

-- 
Darren

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