[Gllug] Long-term storage of digital photographs

[Peter Grandi]

>>> On Tue, 19 Jul 2005 08:05:39 +0100, John Winters
>>> <john at sinodun.org.uk> said:

john> I have a steadily increasing collection of digital
john> photographs on my hard disc, and I can see the time coming
john> when I want to move some of them off to make space for
john> other stuff.  Not so much due to a lack of disc space as a
john> lack of backup capacity.  I have a 35G DLT drive, but even
john> that will be too small within the foreseeable future.

Just about the only cost effective way to do backups nowadays is
to hard discs. When I buy hard discs I always buy them in threes
or fours, the extra two or three purely for offline backup (but
note that while they have the same capacity I ensure each is
from a different manufacturer).

Some people think that hard discs are fragile, and this may
apply to discs that are powered up and spinning. But hard discs
at rest are amazingly resilient and long lasting. Tapes can
stretch or break or get tangled,, tape formats can become
obsolete, ...

I have put together a poor man's external hot plug backup
''device'', by the slamming together of a cheap external 5.25"
FW box and a cheap 5.25"-3.5" caddy:

   http://WWW.sabi.co.UK/xart/I/hwExtSlotDisk1.jpg

john> What would the team recommend as a medium for long-term
john> archiving of digital photographs?  I would like to be able
john> to go back at least 20 years [ ... ]

I have quite a few things older than 20 years, and on hard
discs; with the decreasing costs of hard discs it is entirely
possible to keep everything online. Offline archiving as such
may well be dead.

john> Do CD-Rs and DVD-Rs have proven data life?

CD-Rs have ''proven'' data life, in that it is quite proven that
it can be either quite short (a few years) or quite long (many
years). DVD[-+]Rs presumably are similar, even if the dye
apparently is quite different chemically.

The main issue is mechanical, how well sealed is the sandwich
that contains the recording layer's dye. Also in many cases the
reflective layer is external, and scratching that makes the disc
unusable.

Apparently the longest lasting are the [-+]RW and -RAM
varieties, as to longevity of the recording layer, which is
not organic, so probably less sensitive to contamination.

But they too have issues of mechanical fragility, in particular
[-+]RW are amazingly sensitive to scratches and use (some [-+]RW
go bad after months).

Cartridge based DVD-RAM is designed to be very robust, but the
capacity is still just 4 or 8GB, and it is sort of difficult to
find cartridge DVD-RAM drives (there is only one that I know is
easily found retail).

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