Tape imaging

[Tor Arntsen]

> On 08/10/2016 07:42 AM, Al Kossow wrote:
>
>> congratulations, you reinvented .tap format.. badly.
>>
>> how did you handle unreadable blocks.

I didn't. I didn't have any unreadable blocks. I have CCTs that I made
(and sometimes got elsewhere) going back to the eighties. No read
errors. I simply needed a way to a) get a copy that I could use to
later write a new tape, with original records, and b) extract the
content when the original minicomputers were gone. And that format
worked for that, and saved all my data. Incidentally it made for an
easy way to create a DLT tape duplicator (via disk) later, when I
suddenly needed one.

In short, it served my purpose perfectly and didn't need any research,
finding software somewhere, port it, blabla. It's a very simple format
which can be implemented and tested in a day, and does the job, unlike
trying to e.g. 'dd' a tape. I don't even need to look up the
'protocol' if I need to write a new tool later. It can't possibly be
simpler, and yet it does the job.

On 10 August 2016 at 17:43, Chuck Guzis <cclist at sydex.com> wrote:
> Additionally, how was the metadata handled?  (i.e. information about
> equipment used, paper labels, maybe a photo of the tape reel itself?).

Paper labels are short. The output file of the above process was
stored together with a 'label file', a short text file with what's
written on the label. And I would sometimes add some extra info if I
looked through the content (with some other software I wrote, and
depending on what the original format was).

I didn't see any need for storing info about the physical tape itself,
e.g. 1600 or 6250 bpi, or reel size. I have yet to find a need for
that.  When I could, I would note (with the label) what kind of
software was used to write the tape (e.g. VMS ANSI tape, or Norsk Data
backup-system format, or whatever). But the important aspect was
simply to have a disk file in a format which reflected the original
written tape, so that the disk file itself could be used to later
extract the content, with other tools. That can't be done with any
format that doesn't store the original record information, except for
record-less formats like 'tar' (record-less in the sense that the
physical record size isn't part of the format, unlike e.g. ANSI
tapes).

For my purposes I also haven't found any need of further equipment
information, e.g. which tape drive was used to read the tape (I only
own one anyway, and I can't see that it would make any difference if I
had more than one). And I also don't need info about what kind of
drive was used to write the tape, there's no way to find out anyway
(other than investigating what was installed at each site at the time
the tapes were originally written).