Looking to read past EOT on DDS/DLT/LTO

js at cimmeri.com js at cimmeri.com
Wed Jan 25 18:06:31 CST 2017

On 1/25/2017 6:07 PM, Charles Anthony 
> On Wed, Jan 25, 2017 at 3:04 PM, Chuck Guzis<cclist at sydex.com>  wrote:
>> On 01/25/2017 02:16 PM, Eric Smith wrote:
>>> On Jan 25, 2017 12:24 PM, "Stan Sieler"<sieler at allegro.com>  wrote:
>>>> We have a friend with a "tape" (DDS, DLT, or LTO ... don't know
>>>> which yet) to which was written a system backup.  Thousands of
>>>> files, with an EOF between each file, and a double EOF + EOT at the
>>>> end.
>>>> The problem: They then accidentally overwrote the start of the tape
>>>> yesterday with about 1 KB of data, plus EOT.
>>> I hope someone can prove me wrong, but I think that short of a major
>>> effort to hack the drive firmware, the data is gone. Modern tape
>>> drives are "too smart" to allow reading past logical EOT, and the
>>> tape format is too complex to allow fooling the firmware by any
>>> simple means.
>> With nothing left to lose, I suppose that one might overwrite the EOT
>> and then kill power during the write, then attempt to read backward from
>> the end of the tape.
>> I've never done it, but who knows?
> Or do  it the data recovery way -- find a broken drive with a working
> transport, hookup a A/D to the tape heads, stream the tape, capture the
> flux, decode.
> Not necessarily easy, tho.
> -- Charles

Would it be possible to just physically 
cut the 1kb + EOT portion of tape out, 
and then attempt to read from 
beginning?  I suppose this would depend 
on how the backup data is formatted on 
the tape (using some kind of container 
format with error checking, for instance).

- J.

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