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From: mancini@maxlab.lu.se (Derrick C. Mancini)
Subject: Re: Saving 100GB of data for 15 years cheaply
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Date: Wed, 9 Aug 1995 09:29:21 GMT
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In article <406st6$8le@gwis2.circ.gwu.edu>, sfearing@gwis2.circ.gwu.edu
(Scott Fearing) wrote:
>        I should warn you of a potential danger of CD storage: CD 'rot'.
>Apparently, the aluminum can oxidize under the plastic protective covering 
>and data can be lost.  This is appearing on CDs as well as laserdiscs, 
>but I assume it does not happen to the special gold plated discs that come 
>out on the audiophile pressings.  There are discussions of this from time 
>to time on rec.video.laserdisc.

I believe, Scott, that your comments may be only applicable to pressed CDs.
The writable CDs are a MO technology, I think.  I am not sure what they
use for reflective coat.   In properly manufactured CDs, the aluminum
should last for 15 years.  It is the presence of water and salts that
cause the damage.  I know I have never seen this effect on anything in my
CD collection, which started when CD's started, about 12 years (and a few
hundred CDs) ago.  By the same token, poor manufacture and improper storage
of tape is far more likely to fail than aluminum in CDs.  In either case,
you would be advised to store in a cool, dry place.  And make duplicates.

Another advantage of CDs is that they are a random access storage device,
which most tapes are not, and should have better ability to recover good
files if a particular sector or track were to go bad.  Many tape systems
will lose the whole tail of a tape from the point a defect is found.

-- 
Dr. Derrick C. Mancini
MAXLab, Lund University         Advance Photon Source, ANL
Box 118, Ole Romers Vag 1       9700 S. Cass Avenue - APS/431
S-221 00, Lund, Sweden          Argonne, IL, USA  60439
Tel: +46 46 222 3355            Tel: +1 708 252 0147
FAX: +46 46 222 4710            FAX: +1 708 252 3222
Email: mancini@maxlab.lu.se     Email: mancini@aps.anl.gov
