[Solar-general] Re: [M-Colab] ¿Agregar unrar-free?

Mie Ago 15 02:30:33 CEST 2007

El Miércoles, 15 de Agosto de 2007 05:45, Sebastian Bassi escribió:
 | On 8/14/07, Diego Saravia <dsa en unsa.edu.ar> wrote:
 | > aunque los guardes bien se descomponen, mas de 10 años no duran
 |
 | Los CDs (CD-R) mas viejos que tengo son del 96-97, y por suerte aun se
 | leen :) Pero lo que me pase a mi es anecdotico, por eso te paso este
 | documento, donde citan al instituto de estandares de USA que han hecho
 | pruebas en camaras donde simulan el paso del tiempo, para hacer luego
 | recomendaciones para las bibliotecas y oficinas del gobierno que
 | guardan datos en CDs:
 | http://www.clir.org/PUBS/reports/pub121/sec4.html
 | En resumen, depende mucho de la calidad del disco (no vas a comparar
 | esos sin nombre que te venden de a 1000 en "la casa del cd virgen" con
 | un Yamaha Gold que viene en caja individual) y de como lo guardes y
 | como lo trates:
 |
 | So what is the life expectancy of a disc? First, we must define life
 | expectancy. For most users, it means the length of time for which the
 | disc remains usable. But that implies some acceptable amount of
 | degradation. How much and what type of degradation is acceptable?
 |
 | With CDs and DVDs, the user does not notice early degradation because
 | the error detection and correction capability built into the system
 | corrects a certain number of errors. The user notices a problem only
 | when the error correction coding is unable to fully correct the
 | errors.
 |
 | One method for determining end of life for a disc is based on the
 | number of errors on a disc before the error correction occurs. The
 | chance of disc failure increases with the number of errors, but it is
 | impossible to define the number of errors in a disc that will
 | absolutely cause a performance problem (minor or catastrophic) because
 | it depends on the number of errors left, after error correction, and
 | their distribution within the data. When the number of errors (before
 | error correction) on a disc increases to a certain level, the chance
 | of disc failure, even if small, can be deemed unacceptable and thus
 | signal the disc's end of life.
 |
 | Manufacturers tend to use this premise to estimate media longevity.
 | They test discs by using accelerated aging methodologies with
 | controlled extreme temperature and humidity influences over a
 | relatively short period of time. However, it is not always clear how a
 | manufacturer interprets its measurements for determining a disc's end
 | of life. Among the manufacturers that have done testing, there is
 | consensus that, under recommended storage conditions, CD-R, DVD-R, and
 | DVD+R discs should have a life expectancy of 100 to 200 years or more;
 | CD-RW, DVD-RW, DVD+RW, and DVD-RAM discs should have a life expectancy
 | of 25 years or more. Little information is available for CD-ROM and
 | DVD-ROM discs (including audio and video), resulting in an increased
 | level of uncertainty for their life expectancy. Expectations vary from
 | 20 to 100 years for these discs.
 |
 | Few, if any, life expectancy reports for these discs have been
 | published by independent laboratories. An accelerated aging study at
 | NIST estimated the life expectancy of one type of DVD-R for authoring
 | disc to be 30 years if stored at 25°C (77°F) and 50% relative
 | humidity. This testing for R discs is in the preliminary stages, and
 | much more needs to be done.
 |
 | > por ejemplo las bacterias se los comen, peor si hay humedad
 |
 | Existe solo un hongo que puede comer una de las capas de un CD, y está
 | en Belice. Al menos ahi ese hongo naturalmente infecta los CDs. Quizas
 | haya bacterias que si las pones en cantidad suficiente sobre un CD te
 | lo estropean, pero no conozco que bajo condiciones normales de
 | almacenamiento haya bacterias que usen CDs como sustrato de
 | crecimiento.

ja

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