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From: Francisco Antonio Doria <>
Subject: [BRAZIL-L] cds degradando-se?
Date: Tue, 23 May 2000 19:36:31 -0000

Silvio Meira é especialista em tecnologia da computação. Consultei-o
sobre a durabilidade de cds e cd-roms.

Doria


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francisco, as opinioes sobre o assunto variam e MUITO. veja as coisas
abaixo;
fiquei com o menor numero - e com a experiencia propria - tenho um quatro
estacoes com a berliner philarmoniker feito em 1985 que nao e mais legivel
hoje - a superficie, em condicoes de alta humidade do recife, foi comida
por
algum fungo...

desculpe pelo tempo para responder - meu tempo esta muito atropelado...

um abraco,

silvio.

-------
esta citacao foi confrontada pelo proprio lab que fez os testes!

Tests by the National Media Lab show that top-quality
VHS tapes stored at room temperature preserve data
dependably for just a decade. Average-quality CD-ROMs
become unreliable--some can be read, some can't--after
five years. And even when tapes and disks remain intact,
the hardware and software needed to read them may no
longer be available.
http://www.usnews.com/usnews/issue/980216/16digi.htm

outra parte da briga diz que...

I will also FAX you a copy of a Letter to the Editor of the Washington
Post
by Deanna Marcum, the President of CLIR, which will give you an idea of
the
Council's agenda. They seem determined to prevent paper and film archives
from going "digital" because digital media does not have the same
longevity
as paper. They apparently see this as a problem. What they fail to mention
is that with proper storage and handling and a transcription plan,
relatively short (20-30 year) media and technology lifetimes do not pose a
threat to the preservation of information, as their "Into the Future"
video
implies.

http://www.cd-info.com/CDIC/Industry/news/email-280498.html
reconhecendo tempos de vida medios de 20-30 anos...

e a kodak diz que...

The official position on the lifetime of KODAK Writable CD and Photo CD
Media
is "We predict the lifetime of
KODAK Photo CD, and KODAK Writable CD Media with InfoGuard Protection
System,
under normal storage
conditions in an office or home environment, should be 100 years or
more." In
our opinion, the official
KODAK statement is well within the legitimate interpretation of this
study.
Under controlled conditions, our
best estimate of the data life of these products is 217 years, which
provides
room to incorporate reasonable
differences of opinion as to what constitutes "normal storage conditions."

em http://www.cd-info.com/CDIC/Technology/CD-R/Media/Kodak.html

MAS termina adicionando que...

All lifetime predicitons are subject to the following caveats:

1.This methodology can only predict lifetimes limited by the failure
mechanisms which evident themselves
at the temperatures and times encompassed by the experiment. It is
always
possible that, at
temperatures closer to those experienced during normal use, a
different
mechanism will have a higher
rate than the mechanisms we have probed, leading to a reduced product
lifetime. The greater the
difference between ambient temperature and the lowest test
temperature,
the greater the likelihood of
this occurring. In order to cause change over the 3 months the discs
were
in the environmental
chambers, very high temperatures were required. ("Clock time",
including
testing and analysis, was
much longer than 3 months. Three month incubations are common in the
optical media industry.)
2.Poor recording or poor playback equipment can drastically reduce the
apparent lifetime of the media.
(The obvious extreme: a broken recorder can create unreadable discs;
lifetime appears to be 0.) It is
very important that the initial BLER be representative of a well
written
disc.
3.The prediction is only accurate if the Arrhenius model is valid over
the
entire temperature range 100°C
to 25°C.

welllllllllllllllllllll...

Cecilia Cavalcanti wrote:

> pra vc!
>
> abraço
> Cecilia
>
> ------------------------------------------------------------------------
>
> Subject: cds degradando-se
> Date: Sat, 29 Apr 2000 06:33:13 +0000
>
> Silvio,
>
> Onde é a sua fonte sobre os cds se degradarem em 15 anos? Um ex-aluno
> meu de doutorado, que trabalha em Stanford, esteve aqui em casa na
> semana santa e me deu de 50 a 100 anos, o que equivale a papel
> vagabundo, com ácido.
>
> Francisco Antonio Doria
>
> Prof. Titular, Fundamentos da Comunicação
>
> UFRJ


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• [BRAZIL-L] cds degradando-se? by Francisco Antonio Doria <>