[9fans] writable optical media

[presotto@plan9.bell-labs.com]

We still have optical media from the start of the project that
is readable.  However, I have no idea how long this media lasts.
Anyone out there know what the record is?  It seems to me the
technology for manufacturing the media changes quickly
perhaps to get price down.

I do know that, as usual, when going back to read old stuff
we found a bunch of implementation errors that caused us to
write part of file A in the middle of file B.  Largely it
was us not understanding the Sony jukebox.  It was interesting
to see vc core dumping because a piece of dennis' mailbox
was embedded in the binary.

Seanq recently copied all our old media into his new compressing
file system and managed to get most of it.  The hardest part
was not the media but the slowly dying previous generations of
optical devices.

I guess the moral is: optical is nice, but when the lifetime of
each round of technology is around 5 years, you have to recopy
every few years anyways since the devices to read the indestructible
media atrophy.  Also, the density goes up fast enough that
copying every few years means that you can always have everything
on line.