Re: Tape, was Single User

On Thu, May 19, 2022 at 11:35 AM Steve O'Hara-Smith <steve@sohara.org>
wrote:

> On 19 May 2022 20:49:51 -0000
> "John Levine" <johnl@iecc.com> wrote:
>
> > The thing in the picture isn't paper tape, it's a 1/2" magnetic tape.
> > It looks relatively new, 1970s rather than 1950s so it is likely
> > recorded 9 bits across (8 plus parity) at a density of 1600 or 6250 BPI.
>
>         I didn't look at the picture. That could be a *lot* harder to read
> even if you have a drive. I've heard tell of tapes that could only be read
> once due to storage damage rendering them more than a little fragile.
>
> --
> Steve O'Hara-Smith <steve@sohara.org>
>
Old magtape can be fragile and the binding agent (glue) that holds the rust
onto the mylar can fail in a couple of ways, depending on the composition
of the tape and its storage conditions. Used to work with a lot of magtape
drives, mostly 9-track, both vacuum column and spring  arm tension. At one
time back in the mid-70s, I recalibrated the servos on a pair of Mohawk
Data Systems drives on  a daily basis. (Good IBM and CDC drives were far
more stable, but not in our budget.)

The best place to get information is at NASA. They stored a vast amount of
magtape with the data from space probes in rooms with no environmental
controls and often rooms that flooded. Years later, scientists wanted to
look at some of this old data and found the tapes to be a mess. NASA
created a program to recover the data and have done more of it than any
organization. If you can track down the information at NASA, that is by far
your best chance. I understand that they have had good success.
-- 
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman@gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683