Hi Sue, While there is some truth in what you have read I have to say that from my researches a two year life expectancy is far to pessimistic. As you can imagine, in our business, we are very concerned with the life expectancy of CDs and so I have done a fair amount of reading on the subject. There are basically two types of dye layer used on CD blanks (that's CD-Rs, not including CD-RWs). Each has it's own advantages and disadvantages - most of which stray deep in the technicalities and which would take far too long to get into here. During the initial development of the CDs technology a lot of attention was paid to the permanence of the burning process and a consensus has been reached on what can be expected for a CDs data retention life. The figures (from memory) are about 50 years for one type and 100 years for the other. Now these are industry figures and are for perfect storage conditions, that is initial burn strength, handling, use, storage temperature, exposure to light etc. etc. Basically, an impractical number, but with a professional quality CD burner, and a reasonable amount of care in handling and storage then half that life shouldn't be unreasonable. (Keep in mind these are all projected figures. CDs haven't been around for that long yet.) One of the strangest things we have discovered is that the more expensive CDs are not necessarily the better from a life point of view. I have checked out some of the more expensive brand name CDs blanks and they are made with the shorter life (50 year) type of dye layer. I have also seen some discount store CDs made with the longer life (100 year) dye. (There is a track on all - well most - CDs which carries this information but you need special software to read it.) The cheap CDs do tend to have more manufacturing errors and some will fail during burning while the brand name ones are better screened for this. However, don't assume that because it costs more it's better. This is CD manufacturer marketing talk. The two to five year life figure may be correct for the re-writable CD-RW disks, after all they are specifically made to be temporary storage. Make sure you buy CD-R blanks for permanent storage. Oh, and the idea of "data shifting" being as problem is just nonsense. The CD drive's laser's positioning on the data track is controlled by what is called a feed back loop. The change in size of the disk due to the rise in it's temperature while you read it would throw off the tracking otherwise. The data is always "shifting" with every change in temperature. It's a very small shift to us but its large when compared to the size of the data track. One of the biggest hazards to the life of burned CDs are strong lights. The dye layer is light sensitive, after all that's how it works. The laser built into the CD burner produces a very very bright spot of light to "burn" the CD initially and it needs to be that bright because the dye layer is is quite insensitive BUT leaving a CD in strong sunlight - or even right next to a bright desk light - for hours on end will gradually burn out the whole of the dye layer so the original laser burn effectively fades out. The second worst hazard is dirt. That shiny side is a true optical surface and the "bits" that are written into the dye layer are incredibly small. A thumb print, a speck of dirt, or a scratch can make several bits of the track unreadable and too many such areas will make the CD unreadable. So where does all that leave you? I would not get too paranoid about re-burning all your data CDs every two years. An archive renewal policy is certainly a good idea but FIRST I would make two back ups not one. Aging is a statistical process so if one CD fails due to aging there is a good chance the second one will still be OK and you can then make two new ones from the old one that still works. If you have the time, and can understand the techno-babble, look on the CD manufacturers web site and see if he says what sort of dye he is using and / or what the life expectancy of his disks is. (Bear in mind the manufacturer will quote idea case life.) Find a nice clean, dry, dark place to store your archive CDs preferably where the temperature remains cool and doesn't vary too much. Put the CDs into storage boxes or paper sleeves at the very least.** Better still find two such places and store one of the your 2 copies of the archived CDs in each place. Don't limit your archiving to just your own burned CDs (although they are most important because they are irreplaceable.) The law entitles you to make a back up copy of any commercial software you buy. What it does not allow you to do is make copies to sell or give away, if you read the license carefully thats what it will (or should) say. All CDs fail eventually (even sooner if you have an accident) so invest in the extra spindle of CD-Rs and take the time to back up all your expensive computer software as well. Renewing your archive every two years? Well if that gives you peace of mind it's probably worth it. Personally I'd probably think more in terms of ten years (provided I had two copies) and I wouldn't get worried until about 25 years. On the other hand there is probably going to be several new types of storage media around by then and you will have transfered all your data to this media because your computer no longer has a CD drive. If you want proof take a look at memory cards and USB "Jump Drives." I'm afraid you can't believe the first thing you read on most technology subjects. Marketing people love to broadcast scary stories like this one, based on extreme interpretations of raw engineering facts, because it boosts the sales of - in this case - CD-Rs. Read the story and take note - as I hope you are doing with this one - and when you've read enough of them decide what you should do about it. A good unbiased source of information on this topic are organizations like the Library of Canada and the Library of Congress. They both are vitally interested in storage of valuable data and both are keeping an eye on the various technologies available. Neither of them are ready to declare CDs as "archival" media yet (i.e., having a guaranteed life of 100 + years) but the Library of Congress is definitely accepting the use of CDs for working copies of data. Do some internet searching - it's quite an interesting topic. I hope this has helped to allay some fears of valuable data leaking away while you sit reading the e-mail :-) Malcolm Archive CD Books Canada Inc. Attn: Malcolm Moody - President P.O. Box 11, Manotick, Ontario, K4M 1A2, Canada. phone: (613) 692-2667 e-mail: malcolm@archivecdbooks.ca Canadian web site: http://www.archivecdbooks.ca From: "Sue V" <genealgal2@execulink.com> Date: 23 January 2006 22:53:35 GMT-05:00 To: CAN-ONT-GREY-L@rootsweb.com Subject: life expectancy of your back-up files Like most of you, whether it is a family photo album or precious family tree research, I back up, back up, back up. Now I'm going to add another feature to my back-ups - a date of purchase written right on the CD and an annual reminder on the calendar to check for reburning needs. Why? CD life is 2 to 5 years according to folks more knowledgeable than I..... From http://computerworld.com/hardwaretopics/storage/story/ 0,10801,107607,00.html "Unlike pressed original CDs, burned CDs have a relatively short life span of between two to five years, depending on the quality of the CD," Gerecke said in an interview this week. "There are a few things you can do to extend the life of a burned CD, like keeping the disc in a cool, dark space, but not a whole lot more." The problem is material degradation. Optical discs commonly used for burning, such as CD-R and CD-RW, have a recording surface consisting of a layer of dye that can be modified by heat to store data. The degradation process can result in the data "shifting" on the surface and thus becoming unreadable to the laser beam. "Many of the cheap burnable CDs available at discount stores have a life span of around two years," Gerecke said. "Some of the better-quality discs offer a longer life span, of a maximum of five years." Check out the website for the more complete article. (Thanks to source Eastman's Online Genealogy Newsletter) Cheerio Sue Visser