Gavin Scott writes:
>This is a classic recurring problem throughout the history of computing,
>especially in business data processing where electronic records must often
>be kept for seven years or more (up to something like 20 years in some
>heavily regulated businesses I understand). It's not hard to keep the
>media around, but keeping a working tape drive along with a computer that
>supports it is quite often nearly impossible or at least outrageously
>expensive.
Okay so far, but...
>A DLT tape is
>good for 30 years storage (or more if you actually keep them in a
>controlled environment).
Not unless you know what's stored on those DLT tapes.
HP doesn't document the :STORE format. ORBiT doesn't document its backup
format. As far as I know, the RoadRunner format isn't documented, either.
So while you might have a bunch of DLT cartridges, a DLT drive and a
computer that can talk to it, you might not have any backups because
nobody can read those data formats.
The problem is a lot worse today, because sophisticated high-speed
on-line backup techniques leave bits of files all over the media, written
in a proprietary format. Just being able to retrieve the bits from these
tapes doesn't mean that you'll be able to retrieve the data, or the files
into which the data were organized. As far as I'm concerned, an ORBiT
backup tape is useless for archival storage, because I don't know what's
on it. A :STORE tape is nearly useless for the same reason, but at least
HP is a huge organization with the usual dedication to saving old things,
like tape format documentation. Sooner or later their archivist could be
persuaded to release it.
It's absolutely ridiculous that the :STORE tape format isn't documented
anywhere. It was documented for MPE/V, after all. The format could be
reverse-engineered by using a number of publicly-available documents,
probably well enough to recover data -- so long as you don't use
compression or interleaving. Compression isn't documented at all, and
interleaving isn't documented well enough to reverse-engineer. But why
should HP make its customers engage in reverse-engineering, or hire a
third party, just to get at their own data?
><plug alert>
>
>One of the products that we sell here at Allegro is XOVER (pronounced
>"crossover") which is an any media to any media MPE tape copier.
...
>In a forthcoming version of XOVER, we'll be supporting archiving of
>multiple tape volume *sets* onto a single new tape set.
Unless this format is publicly documented, it's dangerous to use it for
archival storage. Once again, you'll have a tape from which you can
retrieve bits but not records or files.
>You can even restore any file(s) from any tape-set on the DLT *without*
>having to first extract the tape-set on to separate physical tapes.
Yes, as long as Allegro is still in business, and as long as you want to
do it on an HP 3000 and not on some machine that Allegro doesn't happen
to have.
></plug>
There needs to be a *standard* archival storage format, robust enough to
handle the storage needs of any operating system. It's certainly not the
case that you'd want to use that format for day-to-day backups, since
there's a good reason for the weird formats: performance. However, backup
vendors should supply a utility to convert their proprietary format to
the standard format, so that computer users have some hope of recovering
today's data long after today's computers, operating systems and backup
utility vendors have disappeared.
-- Bruce
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