Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
> The summary is essentially to forget it. Some testing with reasonably
> conditions (dark cupboard) had unreadable media as soon as 2 years
> after writing.
>
> The problem seems to be that durability varies widely and there is no
> way for ordinary users to asess media and writing quality (yes, a good
> CD-R medium can be badly written and die early...). Mentioned
> alternatives are CD-RW (not dye-based, lifetime unknowen), DVD+/-R
> (wishful thinking IMO, it has the same problems as CD-R), MOD
> (phase-change, lifetime >50 years, but expensive), tape designed for
> long-term storage (lifetime ~30 years, but this is not any of the
> ''cheap'' tapes like DAT) and keeping multiple copies with constant
> checking and copying.
Basically, use Mitsui Gold CD-R discs for the longest possible shelf life.
Otherwise, even the silver discs I have from 10 years ago are still
good. Only two out of thousands have gone bad in that time and the rest
of the discs are still readable w/o errors -- all stored in cold storage
w/o light exposure in a box.
---
http://www.silverace.com/dottyspotty/issue12.html
This issue contains advice on selecting quality CD-R discs to use when
recording/storing imporant data and photos for long-term storage.
0. Don't use CD-RW discs! They're only designed for short-term storage,
and are erasable. Don't go putting your imporant photos on these!
1. The dye used is probably the most important for long-term stability
and lifespan.
There are three dyes used today in CD-Rs, in order of preferece.
A. Phthalocyanine - inherently stable unlike cyanine dye which must
be stabilized by the addition of other metals, etc. Longest lasting
under testing. Expected lifespans exceeding 200+ years when coupled
with gold reflective layers in cold storage.
(color, light green on silver reflective surface; light
yellow/green on gold reflective surface)
B. Azo. Only Mitsubishi/Verbatim makes this. Up to 100 years,
less stable than Phthalocyanine dye, but more so than cyanine dye.
(color, very deep blue on silver reflective surface)
C. Cyanine dye. Chemically unstable alone, and must be stabilized.
Still, less stable than the other dyes in long-term simulation tests.
However, the first made consumer CD-Rs used this and is part of the
'standard' all CD-RW drives must be compatible with.
(color, green-blue/blue on silver)
2. You can use CDRIdentifier to read the dye information stored on the
CD-Rs you buy as well, which is more reliable if you don't know which
bottom colors represent which combinations.
CDRIdentifier:
http://www.gum.de/it/download/english.htm
3. Besides dye, the reflective layer used affects long-term storage
lifespans.
There are three known types used today, in order of preference:
A. Gold - yep, expensive, but from the bottom, it'll look like real
gold.
B. Gold + Silver - Only Kodak Ultima Silver+Gold CD-Rs use this.
Their tests suggest this combination lasts longer than silver-looking
only discs.
C. silver. - not true silver, but silver looking. Most discs
produced today use this. However, given that metals except gold
corrode, corrosion of such surfaces (when the top laquer layer has been
removed/scratched) can and will occur.
4. Do not look at the top when trying to determing reflective layer
type! Look at the bottom in particular, the exposed areas around the
rim and inner hub. The fake 'gold' layer they put on top of some CD-Rs
are not true gold at all, and only there to 'fake' the customers.
5. The longest lasting CD-Rs, based on longevity testing, use
Phthalocyanine dye and Gold reflective layers. Phthalocyanine with
Gold&Silver reflective layers next, followed by Phthalocyanine and
Silver and Azo and Silver. Cyanine on anything (only silver today) is
the worst performing disc.
6. Typically, Japanese made CD-Rs tend have better quality control, IMO.
Once they move production to Taiwan/Mexico, forget em.
Top Quality Name-Brands, in order of preference:
A. Mitsui Gold CD-R & Kodak Gold Ultima - Phthalocyanine dye + Gold.
B. Kodak Gold Silver+Gold - Phthalocyanine dye + Silver & Gold.
C. Mitsui Silver, Ricoh Platinum - Phthalocyanine dye + Silver.
D. Mitsubishi/Verbatim - Azo + Silver.
E. Taiyo Yuden - Cyanine + Silver.
7. You can get these at www.cdrexpress.com and www.memorymedia.com.
Use www.silverace.com/smartpig/ to locate more places to buy, along with
online coupons, rebates, and ways to save money online.
8. All the other 'cheapies' not mentioned above are generally of poorer
& more variable quality. eg. those $15 / 100pk of no-name CD-Rs at
www.microcenter.com and www.compusa.com are the worst in long-term
longevity.
However, even the quality of cheapies today will last a few years
before deteriorating (assuming no long sunlight exposure; a few hours in
the sun will kill discs) and will work fine. Great for disposable
burns, music, and stuff you don't care if they fade away soon.
The poorest performing brand-name disc above, 6-#E, will still last
10-20 years in cold storage w/o any problems at all!
Remember to keep them away from sunlight/UV, and that most likely,
you'll be moving all of the data off CD-Rs onto newer storage medium
(maybe DVD-R? Holographic?) in 10-20 years. Why? Not one storage
medium has lived that long, and realistically, you'll want to move the
data off obsolete storage media =before= they stop making the drives!!
Just like nobody has 5 1/4" (or 8/12") floppy drives anymore,
expect only to need at the minimum discs that'll last until you migrate
the data off them in 10-20 years from now. Of course, higher quality,
longer lasting discs 6-#A-#D will only help your peace-of-mind.
9. Burn at least two copies of every important piece of data.
Preferably, to two different brands of discs, and preferably two
difference types (eg. Picking #A always is a good #1 pick, anything from
6-#B-#E as your #2). Although simulated longevity tests suggest #A has
the best lifepsan, nobody has ever sat around long enough yet to see if
that's true (in fact, CD-Rs have been out only about 10-15 years!).
Best to make sure you use two different brands and types to keep
bad-batches and combos of dyes/layers from ruining your data years from now.
10. Double-check all imporant discs after each burn - make sure they
match the original files 100% before putting them away and assuming
they're good burns. Use the CD-R program's 'verify-after-write'
feature, available in only some programs, or CDCheck:
http://fusion.zejn.si/ to do this.
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