Tape dumping programs for Unix/Linux..

From: Douglas H. Quebbeman <dquebbeman_at_acm.org>
Date: Thu May 2 15:56:01 2002

> On Thursday 02 May 2002 14:51, you wrote:
> > > At the portion of the work where you just want to get the stuff
> > > spooled to a file, you dont care about "block size" yet, you
> > > just need to get it pulled off.
> > >
> > > Unix will treat any device as a stream of bytes
> >
> > And therein lies the problem.
>
> You would rather work the drive to death ?

When I break it, I fix it. I'm good at things like that.

> You know, any really old tape you are attempting to recover
> you really do not want to be running it thru the tape deck
> very much

For tapes that far gone, a digital read won't work. You have
to build your own drive and sample the analog data coming off
the heads using A/D and not using the digital-based discriminator.

For tapes not that far gone (like the ones of mine that spent
days under water and then months with stachybactris growing on
them), I have a wet-read technique that prevents most shoe-
shining.

> disks are huge these days, and the content is best messaged
> on a new disk rather than an old tape.

Agreed, *that's why the TAP format exists*, as well as Stan
Seiler's tapedisk/disktape system.

> > > Do you see what im getting at here ? hello ?
> >
> > No, I don't, because your entire example was disk-centric,
>
> Wrong i used it as an example, the raw stream already fit
> its intended destination in the hard drive case.

If the structure of what is on a tape depending only on the
bits written to tape you would be right. BUT IT DOESN'T!!!

Record marks on a tape are lengths of tape where NO BITS ARE
RECORDED. Your technique gets the bits, but misses the are-not-bits.

> > Tell you what... how about an empirical test?
>
> Well since we already know the behavior, we already know
> the results dont we ?

Dictionary Definition of "Empirical"

1.a. Relying on or derived from observation or experiment.
  b. Verifiable or provable by means of observation or experiment.

Verification. Proof. Why not put your money where your mouth is?

> > Go buy a 9-track drive and hang it on your *nix box.
> > Let me send you a 9-track tape. You read it any way
> > you want. You send me the tape back.
>
> > Then you go get a second tape, and put the data back on
> > any way you want. Then send it to me, and I'll tell you
> > if your technique works or not.
>
> this is very predicatble if you know the raw behavior
> of the devices isnt it
>
> the whole idea was to point out some of this raw behavior

Crambe repitita.

-dq
Received on Thu May 02 2002 - 15:56:01 BST