ED#111 : Checked Your CD-Rs Lately?

In the past, hard disk drives were small (in capacity) and costly. In 2001, the largest capacity available in a desktop hard disk drive was just 100 GB. More importantly, it would set you back about US$ 450, which was a LOT of money in those days! Needless to say, most users had to settle for hard disk drives of 20-40 GB in capacity.

To make up for the lack of affordable storage, many turned to CD-Rs. Even with an initial storage capacity of only about 650 MB, the CD-R was cheap and one could buy hundreds of them to offload files stored in the small hard disk drive. CD-Rs became an even more popular storage medium when larger capacity 80 mins (700 MB) discs became commonplace, and overburning was introduced.

As it became common to store backups and personal pictures, videos, etc. on CD-Rs, the lifespan of these discs became a concern. According to manufacturers, CD-Rs should last for decades. Some even quoted an upper limit of 120 years based on accelerated aging tests! That sure is a long time, isn't it? But will CD-Rs really last that long?

Update @ July 24 : Added both a new page detailing some tips on improving CD-R longevity, and a new page on reader feedback. We also increased the results to 208 CD-Rs.

Update @ August 4 : Added 154 additional CD-Rs dating from 1999 till 2003, and revised the article to reflect the updated results.

Update @ August 25 : Added 70 additional CD-Rs mostly dating from 1999 and 2003, and revised the article to reflect the updated results.

Time To Go Back To The HDD

Recently, I started porting my archive of over 300 CDs to the hard disk drive. Not only have hard disk drives really expanded in capacity (2 TB per drive and still growing!), they have also dropped a lot in cost per GB of storage, making them one of the cheapest storage options available today. The biggest advantage, of course, is much easier access to the files as you no longer have to look for the CD/DVD containing the files you want and load it into the CD/DVD drive.

How Many Were Still Working?

Interestingly, this exercise also led me to examine the reliability of CD-Rs, as I had never actually thought about their lifespan until now, especially since the oldest CD-R dated only to 1999. That's only 10 years old. I had also taken the trouble to keep them in a cool, dark place. However, the results of the 362 CD-Rs were really surprising. Take a look.

Do note that a CD-R is considered "corrupted" as long as one or more files in the CD-R cannot be read. Discs are labelled as "difficult to read" if it cannot be read by one of the two CD/DVD drives we used for the tests.

Also, this isn't a properly "calibrated" test in that the samples are based on a mixed bunch of CD-Rs - from cheap no-brand CD-Rs all the way to premium Kodak, Ricoh and Imation CD-R media.

Of the corrupted CD-Rs, many of them only had a few files corrupted, but five of the CD-Rs were completely unreadable. Neither one of the two CD/DVD drives we used could even recognize the CD-Rs, much less read anything off them.

After testing over 430 CD-Rs, a pattern has emerged. The rate of failure progressively grew worse over time. The oldest discs, a full decade old, were incredibly bad. They had an extremely high rate of failure - 18.5% were unreadable to some extent with another 7.4% that were difficut to read. The discs from 2000 were relatively good with a failure rate of just 5.9% (with a similar rate for reading difficulty). Of course, those two vintages had the fewest number of samples and the actual results may change radically with a larger sample size.

The failure rate remained steady at 6% for the discs from 2001 corrupted, followed a drop to just 3% in 2002. However, the failure rate increased in 2003 to 6.5% with a whopping 18.2% of the discs difficult to read. It is rather surprising that CD-Rs that were just 6-7 years old were experiencing such failure rates.

The brand of CD-Rs used appears to have some effect on their reliability. Branded CD-Rs from the likes of Kodak, Ricoh and Imation were generally more reliable than cheap, no-brand CD-Rs. The latest batch of no-brand CD-Rs from 2003 were the main reason for the marked increase in the number of discs that were unreadable or we had difficulties reading.

However, buying premium CD-Rs was no guarantee of reliability either. A significant number of premium CD-Rs still failed after just a few years in ideal storage conditions (cool, dark and dry). So buying CD-Rs based on brand alone is no guarantee they will last even a decade.

What Does This Mean?

It should be pretty obvious by now - CD-Rs don't last forever. Although manufacturers may quote lifespans of decades in length, they are unlikely to last more than a few years. Our simple test showed that even when stored properly, CD-Rs that were just 6-7 years old were failing at a significant rate. Of course, how significant it is to you would depend on whether you used CD-Rs to store replaceable files (downloaded media) or critical files (family photos and videos).

Now, we are not saying that all CD-Rs will fail within a few years. It is likely that some could potentially still be readable decades from now. However, you can bet your last dollar that at least a percentage of your CD-Rs will fail after a few years. So what's the moral of this article? If you have something important to keep, back up OFTEN and use MULTIPLE storage options!

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