Psuedo-scientific study of CD-R data longevity:

SNGX1275

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Psuedo-Scientific study of longevity of CD-R data:

I have a stack of 50+ CD-R disks that I filled with data during my undergraduate years, so most of the disks are going to be 11 years old plus or minus 2 years. I'm currently attempting to copy the burned disks back to my hard drive by simple drag and drop copying within Windows 7. I'm using an HP dvd640 drive to read the disks. I do not remember with which burner various disks were burned with, and that may influence results somewhat.. I know that the disks were burned with at least 2 burners, the first was a old DVD drive with CD burning capabilities, it came with an HP tower that I bought in 1998. The other drives were a Philips 4x cd burner and a Pacific Digital 8x. However, I do not know which drives burned which disks, so since I don't have that data I'm only focusing on the success rate of reading all the files burned to particular branded CD-R media.

So far the results are: (brands listed with as much information as is given on their label)

Because of the way this board handles spaces, I can't make it look nice. So the results are going to be presented as:
Disks Successfully Read / Disks Attempted / Notes

Staples 700MB CD-R 15 / 15 / ~300KB/Sec read rate on some
Unbranded no label 8 / 8 / Appear with data on them, but none in explorer
PNY 700MB 16x 0 / 1 / Tiny star like blemishes on bottom
HP 52x CD-R 1 / 1 /~300KB/Sec read
Imation 650MB 8 / 8
Prime Peripherals 700MB 4 /4 /~300KB/Sec read on a couple disks
Memorex CD-R 700MB 2 / 3 / Likely a surface blemish

Summary is, only 2 disks failed to be read and one of those was likely due to physical damage rather than deterioration over time. Seems like if you take reasonable care of your disks (stacked or sleeved) and keep them out of the sun, then you can probably expect the disks to last 10 years. I don't have DVDs this old, so the success rate after 10 years on DVDs may be different due to much tighter tracks.
 
I have also hundreds of burned CD/DVD's, some of it are pre-Windows 95 and still readable.. I've observed that when stacked horizontally /edit- not vertically/, the ones at the bottom are the first to be non-readable. Those with cases lasts longer. So when I put then on a sleeved bag that fits about 40 or 80 CD's, they are oriented vertically, like books on a library.
 
I wish I would have noted specifically which disks had to be read at slow speeds, then I could revisit this yearly and see if they start having unreadable parts. I've got a ton more disks that I didn't attempt to read, if I get bored again I'll test some more. I know that a couple of the first disks I tried failed, but I didn't decide to start recording successes/failures until several disks in.
 
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