RE: Archival storage was RE: [APML] Film vs Digital - Misconceptions!!!

["Gene Horr" <genehorr@houston.rr.com>]

> -----Original Message-----
> From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
> Behalf Of Jeff Ball
> Sent: Tuesday, December 31, 2002 2:04 AM
> To: astro-photo@seds.org
> Subject: Archival storage was RE: [APML] Film vs Digital -
> Misconceptions!!!
>
>
> John mentions something that I have a question about.  I have been reading
> some articles on the unreliability of CDs as a long term storage medium.
> Especially when exposed to light.  Are there CDs that are tested and found
> to be more reliable than others as a storage medium?

Well, I'm having to go back several years to remember the exact figures,
but IIRC "burned" cd media has an estimated lifetime of somethink like a
couple of decades.  The recommendation was to copy everything once a decade
and you should be safe.

"Stamped" (commercially produced) media had a much longer shelf life.  Close
to a century IIRC.  But many of the inks that were used in the past would
start disolving the disk from the backside.  This generally isn't an issue
to us as we aren't stamping 1,000's of disks, but you should have copies of
your software master disks due to this problem.

Magnetic tape can become corrupted by magnetic fields, cosmic rays,
oxidation,
and probably other things that I am not thinking of.  Climate controlled
storage in a metal case theoretically could have a media life of several
decades, but I find errors occassionally creeping into media that is only
5 years old.  I recommend making a new copy at least every decade.

In addition you want multiple copies.  Archive each month's backups and make
at least two copies - one for at home and one in a safe deposit box.

> Are hard drives the most reliable?

IMO the least.  While I do have drives still in operation that are over a
decade old the recent models of consumer drives have a disturbingly high
failure rate.  If subjected to heavy use only count on 3 years lifetime to
be safe.  If a Fujitsu change it out _now_!  Their reported failure rate
was something like 25%/year.


Gene Horr
genehorr@texas.net



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