Re: Softdisk

[Eric Smith <eric-no-spam-for-me@brouhaha.com>]

Wayne Stewart <waynes@intergate.ca> writes:
> I wouldn't necessarily count on them
[3.5" disks]
> lasting longer than 5.25" disks.

Quite true.

> Using various means I recovered 
> most of it, bought a CD burner and put them on CDs. I guess I really
> should do the same with my own floppies.

Good plan.  By the way, you shouldn't necessarily count on CD-Rs (or even
pressed CDs) lasting too terribly long either.  Over time oxygen seeps
through the lacquer on the top surface of the disc, and oxidizes the
reflective layer (alumimum in most pressed CDs, silver in most CD-Rs).
When the metal oxidizes, the reflectivity changes considerably, such
that the data can no longer be read.  This is a gradual process; at
first there are just more correctable errors.  You don't find out about
it until there get to be enough errors that they overwhelm all three
layers of ECC coding, and by then it is too late.

On a properly manufactured disc, stored in reasonable environmental
conditions, this will take quite a few years -- usually more than 20.
Most of my audio discs from 1983 and 1984 still play OK, although the
correctable error rate is now a fair bit higher than the Red Book spec
allows for newly manufactured discs, so there is definite evidence of
degradation.  And only a fool would bet on CD-R media being manufactured
especially well, given the prices they sell for now.

CD-Rs using a gold reflective layer are expected to last much longer,
and this is borne out in accelerated aging tests.  Unfortunately CD-Rs
with a gold reflective layer are expensive and difficult to find.

I'm completely unimpressed with Kodak's mixed gold/silver discs.  The
gold content is low enough that when the silver oxidizes it will still
be unreadable.

My recommendation for anything that you want to keep for a long time
is to write it on several gold CD-Rs, and plan to make a fresh copy
(and compare it bit-for-bit with the original) every 10-15 years.
Ideally copies should be stored in multiple locations, in case
unexpected environmental conditions in one location cause a catostrophic
degradation.

Is your user group library CD available for purchase?