On Tue, 2010-04-27 at 14:56 -0400, Sean Dague wrote: > On 04/27/2010 11:11 AM, Joseph Apuzzo wrote: > > > > > > Backups are only as good as your media. My general understanding of > consumer writable CD/DVD discs is they are really only rated for a > couple of years, after which point your mileage may vary in your ability > to get data back off of them. > > I assume the rule would apply to blueray as well, as it seems to be > roughly the same kind of material. > > -Sean > Here's another point of view, taken from: "Care and Handling of CDs and DVDs: A Guide for Librarians and Archivists"
http://www.clir.org/pubs/reports/pub121/sec4.html " 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. " (Found via Google search: "optical discs" stability. I once downloaded a 2004 NIST study entitled: Stability Comparison of Recordable Optical Discs). I used to follow a Usenet forum on recordable CDs. A point often made there (as Sean stated above) is that media quality is highly dependent on manufacturer. Highly recommended is Taiyo Yuden or any media labelled made-in-Japan. Certain made in Taiwan brands had a reputation for being cheap junk. > _______________________________________________ > Mid-Hudson Valley Linux Users Group http://mhvlug.org > http://mhvlug.org/cgi-bin/mailman/listinfo/mhvlug > > Upcoming Meetings (6pm - 8pm) MHVLS Auditorium > May 5 - Crack and LLVM > Jun 2 - Android > Jul 7 - Patent Absurdity - The Movie _______________________________________________ Mid-Hudson Valley Linux Users Group http://mhvlug.org http://mhvlug.org/cgi-bin/mailman/listinfo/mhvlug Upcoming Meetings (6pm - 8pm) MHVLS Auditorium May 5 - Crack and LLVM Jun 2 - Android Jul 7 - Patent Absurdity - The Movie
