Re: [ARSCLIST] "Archival" DVD-R?

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Dear All (and this means the archiving community in its broadest sense),

we are constantly bombarded with discussions of stability of Recordable
Optical Media, all very responsible and well-documented - I do not mind to
plug:

> Joav Shdema:
> I have the following very current PDFs that deal with the subjects we
> discuss here:
>
> 1) Stability Comparison of Recordable Optical Media
> 2) Discs?A Study of Error Rates in Harsh Conditions
> 3) Care and Handling of CDs and DVDs ?A Guide for Librarians and
> Archivists
> 4) DVD-ROM Drive Compatibility Test for DVD-R(General), DVD-RW, DVD+R,
> DVD+RW and DVD-RAM Discs

----- however, there are TWO trees that we need to bark up:

 - the tree that everybody is already dealing with

 - a stable CD or DVD is worthless if there is no equipment - drive - that
will read it. It does not matter if incompatibility between drive and medium
only develops over time - the result is worthless in any case.

----- I have not seen any work reported on the long-term performance of
drives. To my knowledge there has been no accelerated aging of drives, no
continuous exercizing of drives until they break down (they do that to IKEA
chairs, you know!)

----- there are several directions that product development takes. Early
generations are often very conservatively built, although virtually no modern
equipment is built that needs maintenance, such as lubrication. Functional
units are replaced instead. Such conservatively built equipment is expensive
in manufacture and in materials. For this reason, product development intends
to replace ceramics, glass, and metal with plastic, and furthermore, more and
more elements are made as complete castings, reducing assembly labor.

----- in a CD player, the original HeNe laser was quickly replaced by laser
diodes. Glass lenses were replaced by plastic. I have not studied this in
detail, but there has been 25 years of development.

----- over the years, I must have disassembled about ten 3½" floppy drives
(from the 720kb of the 1980s to 1.44 Mb of the 2000s), and the experience has
not been happy. Just as an example: where the carriage for positioning of the
reading head originally had brass (or bronze) bushes sliding on a polished
steel rod, that was replaced by plastic. Plastic may distort with time.

----- I have also disassembled a number of hard drives. Inside, everything
seems to be professional quality, no plastic, except where relevant for
weight and insulation, and precision ball bearings

----- in terms of DVD or CD drives: will the surface of the lens corrode with
time and temperature? Will the material cloud? Will semi-reflecting coatings
corrode? Will the carriage warp? Is there anything like "purple plague"
regarding integrated circuit termination anymore? Mothballing may not be the
answer.

----- in conclusion I would like anybody who feels the urge to undertake
"stability tests" on optical disc media, to take the appropriate drives to
their local engineering department and to discuss the actual mechanical and
electrical design. You will receive explanations for why a particular
material and configuration choice was made, and you will have a sparring
partner who will be able to predict performance under stress.

----- I fear that you will discover that you can only trust optical media
while the current generation of media and equipment is industrially
supported. Say five years, to be conservative.

----- I shall not respect future analyses of longevity, unless it is a system
analysis, not a medium analysis. I know that it is much more expensive than
leaving your discs out on your desk or in a car and monitoring the
progressive problems. But without a drive, all we preserve are mirrors and/or
optical gratings.

Kind regards,


George