Electronic Media Storage - What is the shelf life of recorded CDs?

F

Fatboy

Need some help from the Cove. A need has arisen to scan and store quality records onto CDs. I was wondering what considerations should be given to degradation of CDs over time? We are required to keep certain records for 10 years and notify customers prior to disposal. Therefore, the retention and quality of the CD should meet this requirement. I suspect that this type of CD may exist but is very expensive.
 

Marc

Fully vaccinated are you?
Leader
I have heard a lot about CDs disintegrating or becoming unreadable over time but I haven't seen any real studies with data. That doesn't mean said studies don't exist, but I have 'standard' CDs that are over 10 years old and I haven't found any yet that have gone bad when I have gone back to get information off an old CD. I do keep them in boxes in a closet in their cases. But then I also have floppy disks kept in the same closet dating from 1986 (about 18 years old now) that I can still read in my floppy drive (I just tried a couple).

Just my experience. Can't speak for others.
 
Fatboy said:
A need has arisen to scan and store quality records onto CDs. I was wondering what considerations should be given to degradation of CDs over time?
Have a look at the following links... I hope they can clarify the matter a bit. As usual it's very much down to how they are stored (Marc's closet seems to be a good bet) ;)

Prolonging CD-ROM's Life Expectancy
Do CDs have a life expectancy of 10 years?
Readability, or When Is a CD's Life Really Over?
How Long Can You Store CDs and DVDs and Use Them Again?
How long will data recorded on CD-R and CD-RW discs remain readable?

The last link could be interesting:

ISO 18921:2002, Imaging materials — Compact discs (CD-ROM) — method for estimating the life expectancy based on the effects of temperature and relative humidity

ISO 18927:2002, Imaging materials — Recordable compact disc systems — method for estimating the life expectancy based on the effects of temperature and relative humidity.

/Claes
 

Wes Bucey

Prophet of Profit
The depth and breadth of knowledge here in the Cove never ceases to amaze me. That was really a fast and comprehensive response, Claes.
 
Y

YankInOz - 2009

Well Claes has given you a really good source list, so start with that. However, my previously career was in the field of Document Imaging & Management (paper & digital) and I would strongly suggest (based on my experience) that you look for redundant means to store your data.

It all comes down to how valuable your data is. If it is valuable, I'd be doing multiple CDs for off-site storage as well as other forms of storage (hey, microfilm is very cheap and in a pinch can be read with lens and candle).

In the early days, the dyes used for CD substrate layers were a bit iffy and, in some cases, very unstable. There have been big changes over the past ten years, but I always found CDs with a Gold substrate were the most reliable.

But as I said, it depends on how valuable your data is.
 

Marc

Fully vaccinated are you?
Leader
That is the key - how valuable is your data? Many times I have burned 2 CDs - 'Just in case...' I have data files and even copies of programs that go back to 1985 - 86. Important floppies I transferred to CD when I got my first CD writer. Before that I wrote them to Iomega bernoulli disks (starting with the 8" 5 megabyte magnetic 'floppies' for any of you who remember them and then to the 20 megabyte 5" disks - both of which internally were flexible disks). If I get nostalgic at some time I'll bore you by recounting my experience with Iomega, Jerome Johnson and the old SF Home Brew club that he came from (the same one Woz, the original Apple hardware designer, was in). I worked as a consultant to Iomega with Jerry Schlagheck when Iomega made their first storage box with SMT (surface mount technology) devices (which is also how I got my early experiences with Ford - and thus 'automotive' {with Ford it was their engine computer}). My life back then was troubleshooting electronics from manufacturing processes to board design and layout to finite analysis of assemblies (another project I was involved in was the Bradley Fighting Vehicle main computer reliability). I still have those and the old Bernoulli box and a computer with the software and scsi interface to run the box - but I did transfer everything off the Bernoulli disks when I got a CD burner so it's toast other than as memories of 300 and 1200 baud days with the exception of hardware and software issues.

I'm telling you this little story because it goes beyond the media to the application and hardware levels. You have to ensure that in 10 years you still have both the software and the hardware to read the archived data. Sometimes it won't matter. E.g.: ACSII (plain text) files from years ago are still readable by many, many applications. But - as an example - I had a version of FrameMaker for Mac from back in 1988 that I wrote my first 'book' in. Today I would be hard pressed to open that file. I'd have to pull my OLD Mac Si out of the closet, set it up again, use a 12" monitor I've saved for use on 'any old Mac' and - hope... I haven't looked at that file in years. Framemaker still makes a Mac version, but I'd bet the current version wouldn't open a file from 1988...

if your data is important to you and time is an issue, remember there is more to it than storage medium.

EDIT ADD: I saw the last post about being redundant. When that is an issue we're beyond archiving. If realtime is an issue you have to have a multiple location setup where a RAID or other mirroring technique is used with a central server so that any time a satellite location drops out a remaining location picks up and distributes the traffic. I am mostly familiar with this with respect to web sites. If my server fails, whether it's a local connectivity issue or a drive failure, how is the 'void' filled? In the case of this site, if a drive fails I do have a backup drive mirroring this one, but it does not 'take over' automatically. And if my connection fails, I have no redundancy. I could do it but the co$t is a bit much. I had an insurance company as a client once - They had a central server and they mirrored, in realtime, to 4 geographically diverse locations. They also had a failsafe for the main server going down including auto-magic domain IP forwarding so even a catestrophic failure at 2 or 3 locations would not seriously affect them.
 

Wes Bucey

Prophet of Profit
As Marc so vividly describes - storage and backups are always related to budget in some way or another. We really need to do Failure Mode and Effects Analysis, mistake proofing, and common sense brainstorming when it comes to making decisions. Ultimately, they all boil down to one question:

"What is the worst that can happen if I don't have this document or a copy at some point in the future?"

If the thought of being without that document is too horrible to consider, then multiple copies in scattered sites seems totally justified.

For almost everything I have, the answer is, "I would miss them and regret their loss, but no document I have is absolutely "life or death" for me or anyone to or for whom I am responsible."

I was also impressed with Marc's words on the importance of having hardware and software to read the computer media. I have an image of some of the old 5-inch and 8-inch floppies (300K? - they really were flexible!) I used back in the early 80's. There may still be some resting in file folders in my garage storage area. I'm pretty sure I don't have any hardware left that could read them. (All my old vinyl records still play, even though scratchy; some of them are more than 50 years old.)
 
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