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03/19/2006 09:05:05 PM · #1 |
So, I read today that CD-R only have a shelf life of a few years. I guess what ever is embedded degrades after a while.
Two questions.
Why don't companies fix this?
Do DVD + R degrade as well?
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03/19/2006 09:11:03 PM · #2 |
There's an excellent section on this Here at Wikipedia.
Bottom line is treat them well and they should last. |
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03/19/2006 09:17:23 PM · #3 |
This reminded me to post this link:
//opinionjournal.com/la/?id=110008086
An interesting perspective. Negatives, slide and prints last a long time. Where will our digital files be in a generation or two?
Message edited by author 2006-03-19 21:17:33.
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03/19/2006 09:43:10 PM · #4 |
I think this is the only real example of stable storage media we have so far -- fortunately it's perfectly suited to recording binary data. With a proven shelf-life of over 3500 years I don't think anything else comes close ...
All new media lifetimes are estimates based on "accelerated aging" tests -- we won't know if a CD-R will retain data for 25 years until one is 25 years old.
The real problem will be the continued manufacture of hardware to read the otherwise-invisible data -- you can see and interpret the data on a negative/slide without hardware) -- and software which continues to interpret the data correctly. |
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03/19/2006 10:56:28 PM · #5 |
can anyone answer my questions?
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03/19/2006 11:08:21 PM · #6 |
I bought my first CD in, I believe, 1988. It was Erasure's The Innocents album. Since then it has been played hundreds of times, carted across the country twice, kept in cars, thrown on desks. It still works fine.
I know our pictures are a little more important, but I lose very little sleep worrying about whether my backup DVDs are quietly degrading in their dark closet where they are never touched or disturbed. It's just not going to happen. No more so than a negative accidently being creased or scratched or lost.
EDIT: typo
Message edited by author 2006-03-19 23:13:07. |
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03/19/2006 11:08:52 PM · #7 |
Because they want to sell you more after they are worn out?
Just a guess. |
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03/20/2006 12:55:27 AM · #8 |
Originally posted by DrAchoo:
I bought my first CD in, I believe, 1988. It was Erasure's The Innocents album. Since then it has been played hundreds of times, carted across the country twice, kept in cars, thrown on desks. It still works fine. |
There is a huge difference between commercially manufactured CDs and recordable CDs like we use for data storage.
A commercial CD is "pressed" and contains "pits" and "lands" -- areas which are physically higher or lower than their neighbors. The laser reads the interval between transitions from one level to the other to determine the data's value.
Recordable CDs use a dye which is changed by the action of a (relatively) high-powered laser; the color changes then simulate the pits and lands of a "real" CD, and the intervals between color changes are read by a lower-powered laser.
The dyes are more likely to change color than for the physical structure of a CD to change dimensions, so pressed CDs are likely to have a much longer life, assuming they don't de-laminate, and there are still devices to read the data. |
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03/20/2006 07:46:47 AM · #9 |
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03/20/2006 09:08:14 AM · #10 |
Originally posted by American_Horse:
anyone?? |
Writable DVD media degrades as well. I've read that RW media will last longer because it involves melting the media as opposed to dyes.
I just make two copies of everything, and keep the disks in a cool, dark storage area. I've never lost any data (yet).
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03/20/2006 01:35:37 PM · #11 |
Originally posted by American_Horse:
can anyone answer my questions? |
The responses have generally already answered your questions as well as they can be answered, but to reiterate and expand a bit.
First no one has "fixed" this because A) No one is sure how much of a "problem" it is, and B) What do you consider a fix?
My personal experience is that cheap discs do seem to have more problems with degrading, I've had cheapies that went bad after a year. I've got TDK golds I bought at 10$ a pop in 1995 that are still good. I've also got cheap media I bought several years ago that are still good. But I take care of them, and I don't rely on them for long term. Next, what do you consider a fix? A reputable company claiming 25 year shelf life when you take care of the discs isn't "fixed" enough for you?
The answer to your second question is yes. All burned media have degredation issues. RW will have more issues then WORM, given the are changeable by nature.
In fact, pressed aluminum layer discs have degredation issues, they will not last forever. The general accepted shelf life under good conditions appears to be around 100 years, but as the CD is only 20 some years old(and early batches had the infamous rot problems) it's hard to say just how long they will last. We might have a mass failur of discs over the next 10 years for all anyone knows.
The real "answer" here is you should not ever expect one piece of media to last forever. Backup your backups. If your data is truly important to you, you will have a plan whereby you freshen your backups(i.e. make new ones) on a regular basis, to be sure that integrety of the media is not a problem. This also means in the long run you'll probably be transferring your media to new standards every so often. I'd guess a good many of us have already made the transition to DVD, and with the BlueRay and HD-DVD specs coming soon, it's not unreasonable to expect we'll be doing it again in the forseeable future.
Message edited by author 2006-03-20 13:40:12. |
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03/20/2006 01:53:12 PM · #12 |
Also consider that in 10 years, data CDs will be hopelessly outdated; even data DVDs will seem small (they already do in some respects). You'll be very wise to migrate your digital files to newer media long before the current media physically degrades.
Personally, I prefer external hard drives; I use two in rotation, one of which is always off-site. One is kept at work, the other is at home. This also means I have two backup copies of both my work files and my home files, since I back up to the same drive at work. If one of these drives fail, I can replace it without data loss, and with confidence that I have another backup. At some point, there may be a better alternative to hard drives, and at that point I will migrate all my files across.
I have some documents (old Word Perfect, Lotus 1,2,3, Quattro Pro, etc.) from as early as 1986 and still can easily find them if needed. I never have to go digging through archives of floppy disks and try to find a system that can read them... I don't even have a floppy drive for my work laptop, and only one of our machines at home has a floppy drive.
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