On 8/14/07, Diego Saravia <[email protected]> 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. -- Sebastián Bassi (セバスティアン) Diplomado en Ciencia y Tecnología. GPG Fingerprint: 9470 0980 620D ABFC BE63 A4A4 A3DE C97D 8422 D43D