On Wed, 05 Apr 2000, Jochen Hoenicke wrote:
> On Mar 27, [EMAIL PROTECTED] wrote:
> >
> > According to the QIC standard (www.qic.org) for these tapes, the
> > tape is split up into 32K numbered segments, with some space used for
> > ECC. ftape says that this results in 29K, although I'm not sure as I
> > get the impression from the specs that it varies.
>
> Yes, it varies, because some of the 32 sectors that make up a segment
> can be marked as bad. These sectors are simply skipped. The last
> three good sectors are used as ECC, the remaining sectors are data.
>
> > The first few segments contain a tape descriptor and a volume table
> > (with some duplicates), which describe the tape name etc, and segment
> > start and end numbers for each archive, along with their name, format
> > etc. Then each archive follows in their allocated places, in the
> > format specified in the volume table.
>
> AFAIK they also count the skipped bad sectors and segments, so it may
> not work if an archive is copied from one tape to another which has
> different bad spots.
Note to Robert: you'll need to check the bad sector map on the two
tapes you're copying; if the destination tape has any bad sectors
which the source doesn't, then copying bit for bit clearly won't
work. You'll need a program to interpret the data, rework it and
write it to the new tape (ie. IDT, or the program I'm trying to
write). IIRC the bad sector map is printed as debug messages by ftape;
I don't know how detailed this is, though.
> [...]
> I don't know what this off by one error in the volume table is. Maybe
> its just a programming error and nobody noticed since there is only
> one single backup software for the Ditto 2GB.
I think someone must have noticed, as the error is cumulative and a
correction must be made, for example, when appending to the tape. IMHO
they noticed and to retain compatibility with old tapes, just added
a calculation to compensate.
> [...]
Robie.
--
Robie Basak <[EMAIL PROTECTED]>
