[semi-OT] QIC2 streaming cartridge tape lossage

[Ben Scott]

On Sat, Nov 28, 2009 at 5:17 PM, Michael ODonnell
<michael.odonnell at comcast.net> wrote:
>>> Nice how the 9-track serpentine
>>> layout makes it possible for a single medium flaw to trash the bit stream
>>> in 9 different places at once...   >-/
>>
>> Unfortunately, I think most tape systems are multi-track --
>> everything from ancient reel-to-reel stuff to the latest LTO.
>
> Right, but formats like reel-to-reel (you know, the ones they showed
> spinning in old timey movies & TV to indicate awesome computing power?)

  Oh, I'm quite familiar with what they look like. One of the jobs
assigned to me at UNH, circa 1995, was transferring archival data from
old 9-track reel-to-reel tape to CD-R.  They were doing this partly
because some of the tapes were approaching the end of their storage
lifetime (they contained satellite telemetry from rockets launched a
decade or two prior), but mostly because the university only had two
9-track units left and were phasing them out.  I remember the CD-R
unit was almost as big as the computer and recorded at 1X (it was a
few years old), and the computer had a dedicated 1 GB full-height HDD
to hold the CD image.  I had to take the tapes down to the machine
room (hi mwl!) and have them mount them, then go upstairs and dd tape
images to a holding disk over the network.  Lather, rinse, repeat.
Fun times.

> So my point is that a single flaw in the tape wouldn't just
> trash your stream of 9 parallel bits at one point but trash your single
> serial bit stream in as many as 9 places.

  Well, I was thinking that either way, you still lose the same amount
of data, but now I see your point that at least with parallel
recording, the damage is likely localized to a single file (block,
record, whatever).  Chances are even a single bit error in a file is
going to cause bad times, so keeping it to a single one counts.  I get
it now.  :)

> Think of a scratch in an LP.

  Yah, like how many people even know what those are these days?  ;-)
The current generation of kids grew up with MP3 players.  Even CDs are
getting to be quaint.  Process marches on!  Well, *something* marches
on, anyway...

-- Ben