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Richard L. Hess wrote:
> Hello, Steve and Stevie,
>
> I have been using the MAM-A Gold DVDs since they came out and am 
> pleased with them, but the last time I checked to answer Steve's 
> question, MAM-A's attorneys are allowing them (or at least did allow 
> them) to claim a 300 year life expectancy for the gold CD-Rs. The gold 
> DVD-Rs I think have only been claimed at an 80-year life expectancy.
>
> The one thing, however, that I think we've learned from tape is that 
> in highly complex chemical products, the anticipated failure modes and 
> failure stimulii are not always the ones that will bring on 
> end-of-life conditions.
>
> We have also seen how batch-to-batch variations in tape can affect the 
> tape's longevity.
>
> Both of these lessons are instructive to the CD/DVD marketplace.
>

There is something to be said for ensuring diversity of media when 
making archival copies.  In order starting from the minimum:
Multiple copies on media from the same batch, same plant.
Multiple copies on media from the different batches, same plant. 
(e.g.different lot numbers.)
Multiple copies on media from the different plants, same process. (e.g. 
media manufacturing company runs multiple plants all using the same 
design assembly techniques)
Multiple copies on media from the same plants, different process. (e.g. 
media manufacturing company runs one plant with separate lines of AZO, 
PHTHALOCYANINE, and CYANINE)
Multiple copies on media from the different plants, different process.
Multiple copies on media from the different plants, different process, 
different company. (e.g. several competing media manufacturing companies)
Multiple copies on media from the different technologies, same family. 
(e.g. CDs vs. DVDs)
Multiple copies on media from the different technologies, different 
families. (e.g. DVDs vs. hard drives vs. SLC solid state drives (SSDs))
Diversity of storage location: another room, across 
town/state/nation/world/off-planet

Each of these avoids a different degree of common cause variation, and 
forms a trade off between maintenance overhead, money, access latency, 
and level of protection.  The LongNow Foundation has thoughts on this as 
well.

-hk