The issues with optical media longevity are related to corrosion/ fatigue of the dye or foil substrate upon which the bits are encoded. Commercially produced audio CDs/DVDs are pressed and encased, promoting better longevity of the media, and they're not as sensitive to bit-errors. CDs and DVDs produced in a burner encode bits as essentially a set of burned spots in a dye laminate substrate and have a shorter life span.
That said, I have CD data media that I wrote in 1995 which is still 100% useable. Data DVDs are as yet pretty young, but I have several I wrote in 2003 (now five years old) which are still in perfect condition. When stored and cared for properly, a decade at least is not unreasonable to expect in life span. But what this does imply is that the basis of digital archiving is replication, replication, replication. Digital information can be replicated infinitely at no loss ... it's just numbers. My primary backup system is sets of twin hard drives now, just added another terabyte drive to the array. Making another duplicate is as easy as "copy disk A to disk B", go away for a day. Run a file system check every now and then to be sure nothing has become corrupted. I consider DVD and CD storage archives as a secondary, backup archive only. They're too small and too inconvenient to handle in volume. I have 260,000 image files in my archives at the moment, growing by 200-300 per week on average and stretching back to 1976 from scanned film. There are several thousand negatives I haven't scanned, most likely will never be. I can find anything that was digital capture or scanned in a few minutes, but finding what's useful in the film archive is a huge job ... and film continues to deteriorate no matter what I do. Godfrey On Apr 2, 2008, at 8:47 AM, [EMAIL PROTECTED] wrote: > I have music CDs that are over twenty years old and still play > well. I don't know if that's the same as a data CD. I have checked > some of my earliest picture file DVDs, which are about five years > old. Thus far, they're all fine. Is there a technical explanation > for why these storage devices wouldn't be semi permanent? The files > can't fade or walk away. At least not so far as I know. > Paul > -------------- Original message ---------------------- > From: Xavier Cremaschi <[EMAIL PROTECTED]> >> Be careful, a cd lives for 10 years, a dvd for less than that (5 >> maybe) >> >> http://le-gall.net/sylvain+violaine/blog/index.php?2007/10/21/31- >> reading-a-10-ye >> ars-old-cd-r >> >> [EMAIL PROTECTED] a écrit : >>> I do back up to DVD. I have several hundred in storage. My five >>> drives give me >> over two terabytes of space. They're about 70% full now. I'll add >> another 500 >> gigs soon. I keep very few backups on drives, save temporary >> backups for >> important jobs. The general backups are almost exclusively on DVD. >>> Paul >>> -------------- Original message ---------------------- >>> From: [EMAIL PROTECTED] (Ralf R. Radermacher) >>> >>>> <[EMAIL PROTECTED]> wrote: >>>> >>>> >>>>> I do work on a Mac, but I doubt that makes a difference. >>>>> >>>> So do I. >>>> >>>> If you get along with 5 hard drives, you just don't have enough >>>> picture >>>> files. :-) >>>> >>>> The problem some of us are having is that we have so much stuff >>>> that we >>>> need to keep some of it (the vast majority in my case) on external >>>> drives which aren't connected all the time or on removeable media. >>>> -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
