Normal (low cost) CD's are unreliable. A normal writeable CD is a layer
of plastic coated with a very thin layer of dye followed by a very thin
layer of aluminum which, in turn, is coated with a layer of laquer (the
painted label). Pressure on the laquer layer (such as with a pen) can
distort the aluminum recording layer underneath and destroy bits.
More insidious is that the thin laquer layer on top is not impervious to
the atmosphere, moisture or contaminants. Eventually the aluminum layer
starts to oxidize (rust) or corrode and your bits go bye-bye.
It is not uncommon for CD's to last as little as a year although 2-3
years is more likely and possibly much longer if they're stored under
exceptionally good conditions. The problem is that you don't know and
you won't know until they suddenly start having read problems.
Since the fundamental problem is oxidation of aluminum the solution is
to use gold which does not oxidize and also use a more expensive and
more stable dye than is used in the typical cost competitive CD. Gold
CD's are available from MAM-A or Kodak but they're much more expensive
than convetional CD's. <http://www.datamediastore.com/goarqucd.html>
Gold CD's probably will last a very long time (assuming you don't write
on the label with a pen) but the cost makes them more expensive than
multiple external hard drives even considering that you should have two
or three identical drives as backup. Keep the third one off-site and
rotate where the drives are stored.
Chuck Norcutt
Phil wrote:
> I was led to believe that the safest method of storage for my images was CD.
> The theory was that any form of magnetic storage (HD) would be less
> relaible.
> Having just read a thread on DP review, many are claiming the oposite and
> that a separate Hard drive is there preferred method and CD's are unreliable
> As all my images
> are on CD I am a little worried, what do you guys use to store you files.
>
> Thanks
>
> Phil
>
>
>
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