The Myth Of
The 100-Year CD-Rom
The Independent - UK
April 21, 02004
Original Article Reference Here
Are we putting too much faith in the ubiquitous "recordable CD", or
CD-R? It is undeniably one of the most useful means of storage around, offering
an inexpensive way to save digital photographs, music and files and costing
less than 50 pence per disc.
If you check the claims made by some manufacturers of popular CD-R brands, you
will see that some make bold claims indeed. Typical boasts include: "100-years
archival life", "guaranteed archival lifespan of more than 100 years"
and "one million read cycles". One company even says data can be stored
"swiftly and permanently", leaving you free to bequeath those backups
of your letter to the electricity company to your great-great-grandchildren.
But an investigation by a Dutch personal computer magazine, PC Active, has shown
that some CD-Rs are unreadable in as little as two years, because the dyes in
the CD's recording layer fade. These dyes replace the aluminium "pits"
of a music CD or CD-Rom, and the laser uses that layer to distinguish 0s from
1s. When the CD is written, the writing laser "burns" the dye, which
becomes dark, to represent a "1" while a "0" will be left
blank so that if the dye fades, there's no difference; it's just a long string
of nothing to the playback laser.
So have you already lost those irreplaceable pictures you committed to the silver
disc? PC Active suggests we should forget CD-Rs as a durable medium, after its
own testing found some with unreadable data after just two years. "Though
they looked fine from the outside, they turned out to be completely useless,"
wrote the technical editor Jeroen Horlings, who had tested 30 brands in 2001,
left them in a dark cupboard for two years and then re-tested them in August
2003. Of the brands tested, 10 per cent showed ageing problems. And it wasn't
just Horlings. After seeing the results, shocked readers contacted the magazine
with their experiences.
Recordable DVDs are not off the hook either. The "dye chemicals" in
write-once DVDs are similar to CD-R, though recording density and disk construction
differ. "We're in the process of testing DVDs and we're sure that the same
problems will occur," said Horlings, who plans to publish his findings
soon.
Gordon Stevenson, the managing director of Vogon International - a company specialising
in data recovery - is familiar with these shortcomings thanks to the experiences
of his customers, one of whom commissioned Vogon to retrieve pictures of his
second honeymoon from a failed six-month-old CD-R. "The dye layer was fading,"
Stevenson says, "but we were able to recover most of the disk. But these
claims [of a 100-year archival life] are unhelpful and misleading. If you're
spending 20p on something, you probably don't expect it to last 100 years,"
he says.
In the wrong conditions, such as sunlight, humidity and upper surface damage,
your CD-R will slowly turn into a coaster. "CD-Rs should never be left
lying in sunlight as there's an element of light sensitivity, certainly in the
poor quality media," says Stevenson. "I wouldn't rely on CD-Rs for
long-term storage unless you're prepared to deal with them as recommended."
Such views are echoed by the National Archives at Kew. "Generally speaking,
we don't recommend CD-Rs for long-term storage," says Jeffrey Darlington,
a project manager at the Archives' Digital Preservation Department. "We
don't regard CD-Rs as an archival medium. Most of the CD-Rs on the market are
not of archival quality." Instead of CD-Rs, therefore, the National Archives
tend to use magnetic tape rated for a 30-year life. Also, they are careful to
copy, check and re-copy to avoid losing information and this is also a useful
strategy for CD-Rs. "If you keep doing that so the CD-R is never more than
physically three to five years old, you'll be safe enough. A hundred years sounds
pretty unlikely," says Darlington.
Not all optical media is vulnerable. The rewritable variants (RW) use metallic
materials that change the phase of the light, rather than light-sensitive dyes.
Commercial magneto-optical and ultra-density optical systems are different too.
Stewart Vane-Tempest, the optical product director at Plasmon, the archival
specialists, has first-hand experience of unreadable CD-R media. "Some
dyes are very robust, but others not," Vane-Tempest says. "The one
thing they have in common is susceptibility to environmental conditions. I do
a lot of digital photography and pay top price for media. If I have anything
important, I generally make a couple of copies. I've not used CD-Rs for long-term
archiving."
Vane-Tempest also offers a tip. Blank CD-R disks have a code that your CD writer
reads to find the best writing strategy. If this isn't in the CD-writer's inbuilt
software (its "firmware"), the default may be a poor compromise. Vane-Tempest
says that some "less scrupulous" Far East companies have been using
other people's codes, with deficient results. However, there is a way around
this which is to find out which brands suit your writer and ensure the firmware
is up to date.
While such matchmaking is useful, there's no way to assess CD-R longevity at
home. All you can do is check periodically. As for whether manufacturers are
guilty of using finger-in-the-air methods, Kevin Jefcoate, the marketing and
product management director at Verbatim, says: "It's a bit more than guesswork
because there's a lot of scientific evidence to back it up."
The answer, Jefcoate says, is to use a climate chamber to accelerate the ageing
of the organic dye. Using a relationship between chemical reaction rate and
temperature, 100-year lifetimes may be argued for normal conditions. Jefcoate
adds that he has never known users to complain of age-related failures? "We
haven't had anyone complain that, after three to five years, it hasn't worked."
It's easy to blame budget CD-Rs when things go wrong. Novatech's purchasing
and product manager, Kriss Pomroy, suggests users buy a small quantity for testing
first.
The PC builder sells unbranded CD-Rs sourced from a Far East distributor that
buys over-production from well-known factories. Are we saving pennies and taking
risks? "No," says Pomroy, "You can get problematic batches, but
that's as true with branded media." The company now sells two-and-a-half
times more unbranded write-once DVDs than CD-Rs.
The world's No 1 supplier of CD-Rs, Imation, talks of "saving precious
digital photo memories" - exactly what many people think they're doing.
Semar Majid, its technical marketing executive, hasn't heard of any ageing problems.
"Optical media should last between 30 and 200 years," he says, "but
it's dependent on storage conditions and how you handle it." He suggests
transferring important photos to DVD, and keeping on moving to new formats.
Another big maker, TDK, takes a cautious view with DVDs, claiming only a 70-year
lifespan. "This does not mean that DVD is more fragile or unstable in time
compared to CD-R; this is only because of the shorter experience that we have
in manufacturing and testing this relatively young technology," says the
TDK product manager Hartmut Kulessa. There have been no complaints about ageing
failures.
As the oldest CD-R is barely a teenager, there are no definitive answers either.
But perhaps the last word belongs to Jeroen Horlings at PC Active. "We
see a lot of manufacturers and they think that quantity is more important than
quality," he says. "The problem will remain."
For more info on CD-Rs and dyes: www.burnworld.com/cdr/primer/whatis.htm; www.xdr2.com/CDR-Info/Dye.htm
© 2004 Independent Digital (UK) Ltd
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