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recover data from relabel tape 3

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a222401

MIS
Nov 29, 2002
21
BE
Hi,
Is it possible
to recover the data from a accidently relabel tape
I had a tape in the robot to recover some urgent data but the operator has relabel the tape.

Thangs
 
Once you've relabelled a tape with Networker, there is NO WAY to restore the data. This is because Networker will write double end of file marks at the end of the tape label, which can not be read after.

You'll need to go to a third party recovery service to get the data off the tape.
 
This is simply wrong and often misunderstood:

- In general, NW can recover each data block.
However, it does make sense to only start at the
beginning of a save set.
- Unfortunately, today's drive firmware does not allow you
to get beyond of the 2 consecutive filemarks that indicate
the logical end-of-tape.

So the key issue is to remove that pattern that represents LEOT.


There are several ways you can achieve this. Data recovery companies can help
(which are very expensive) but you can even do this with native NetWorker.
Be aware that using the second method will loose some data !!!

And this is how you need to proceed in general:
- You better use a stand-alone drive for this purpose
- Mount the media
- Start writing a new save set
- As soon as you see &quot;writing at <data_rate>&quot; in the
device monitor
switch off power. This ensures that NW cannot write another file mark.
- Resync the system and mount the tape.
- Use scanner to find out where the next, good save sets
will begin.
- Rescan the media/recover the data from that physical
location. Use scanner to position there.

The doc TIDS_2002.PDF (available from Legato's PartnerNet) actually describes the routine
very thoroughly.

Be aware:
- This method is not supported (but it seems to work!)
- You should try that several times before you use it for
your 'hot' media.

 
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