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A software or tool to recover formated lto Tapes

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I sent an email to the Archiware P5 company to get more information regarding how the tape is written and if they have any suggestions. Here is what they say:



I am afraid that is not possible:

During labeling, a new "label" is written to the beginning of the tape.
When writing to tape, the drive adds an EOD (end of data) after the written data.
The LTO consortium is now very strict in making sure that reading a tape after the EOD
mark is not possible. As a consequence, there is no drive firmware that is capable
to read after EOD.

There are some companies like OnTrack who may be capable to read such data, but that
must be very expensive as we had a few cases like this in the past and we never heard
about a case where this was done (as we assume we well need to assist when it comes to
extract the data from the the block format of P5).

There is a second reason why this is probably not possible:
While we regard a tape as a linear storage, it physically is not that linear. The drive
writes tracks while moving forward and backward on the tape. An LTO-5 tape for instance
has 1280 tracks, and while writing the first track, the drive's erase head will clear
all tracks in parallel. That means on an LTO-5 tape, you will have after labeling
1280 erased sections in the data, each section at least as long as the label area (a few 100 Kb).

Regarding your questions:
> 1-are the tapes partitioned while labeled .
> so that , there is partition for label/index and other for data (like LTFS) ?

No, the tapes are not formatted in standard (non LTFS) format.

> 2- how many bytes does the label takes and where the data starts if
> the tape is one partition?

The are a few hundred Kilobytes, as there is a tar file at the beginning of the label.
But you cannot position on a tape in bytes, but in file marks. These are marks written
by the drive. The data after the label is at filemarks 11. On a linux box you could get there
mt -f device fsf 11
however you will see that is where the EOD mark is.

> 3- what is the format of the data on the tape (tar or something else )?

P5 uses a proprietary block format, blocks have constant size (in version three one block was 32 KB),
the blocks contain file metadata and the files itself, possible followed by further blocks which may
contain further data of the same file.

In case you would get so far that you get the data blocks from the tape (what I don't expect),
it may make sense to contact us for extracting the files from these blocks.



Does this ring any bills? 



Topic starter Posted : 09/11/2020 10:36 pm
Senior Member

Thanks for the update.  It actually confirms my first response.

Posted : 09/11/2020 10:54 pm
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