Hello,

08.09.2008 20:41, Nikola Pavković wrote:
> Hi,
> 
> I accidentally made a "mt rewind && mt weof" on one of my tapes so that
> bacula does not recognize it as a bacula volume anymore, however the
> data on the tape should still be present.

Bad, but up to this point, there's a chance to recover most of the data.

> I tried several things but
> could not get past the eof mark on the tape. Last thing I tried is label
> the tape once again

That probably destroyed more of the data.

> (had to remove the volume entry from the catalog),
> and do a "bls -V VOLNAME /dev/nst0", but the tape does not move and the
> command waits forever.
> 
> Is there any chance to recover the data that is on the tape, which is
> located after the label mark?

Well, once you get the data off the tape, you can try to recover it 
with bextract and it's -p switch.

Getting beyond the existing end-of-tape mark is the difficult thing.

What you tape data now looks like is

Bacula volume header | EOF | EOF | incomplete block of Bacula data | 
complete blocks of Bacula data

The task is to get the tape drive to read beyond the two EOFs, which 
are translated to and end-of-tape mark.

You can try the following:
Load the tape into the drive
verify the current situation using bls and mt: There should be a 
bacula label and noting more, and after a 'mt -f /dev/nstX eom' you 
should be at file 1 on the tape.
If that's the case, try to write some data to tape and do not write an 
EOF mark, like 'dd if=/dev/zero bs=65536 count=4 of=/dev/nstX'. Be 
sure to use the non-rewinding tape devices (in this example, typical 
linux device names; yours might differ).

With some luck (and depending on what the tape drive, SCSI driver, and 
tape driver actually do...) you end up with something like
Bacula volume header | EOF | 00000... | incomplete block of Bacula 
data | complete blocks of Bacula data

Then try if you can get the tape drive to space further into the tape: 
'mt rewind && mt fsf 5' for example. If that works, you can try your 
luck with bextract.

You'll lose some of your data in any case, but the remaining 99.999% 
of an LTO-4 tape might be worth that :-)

Alternatively, use a data recovery service - they claim to be able to 
read data beyond EOD marks, though I've heard stories that they can 
not always.

Arno

> 
> Thank you.
> 
> Nikola Pavkovic
> 
> 
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-- 
Arno Lehmann
IT-Service Lehmann
Sandstr. 6, 49080 Osnabrück
www.its-lehmann.de

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