CD / DVD Data Rot

How reliable are CD's and DVD's as backup? Well... somewhat.

I had to restore media from way back, all stored on CD and DVD before (external) 500GB+ harddrives became affordable. I've been copying almost all of the material back to HDD, and here are my results... This isn't too scientific :-) just my personal experience with several brands...
 

Drives

First, I am using three different DVD / CD drives to read the disks:

- external USB Liteon eTAU108
- internal IDE Sony Optiarc DVD RW AD-5170 ATA
- internal SATA (reported as SCSI) Hitachi (Dell) HL-DT-ST DVD+-RW GSA-H31N

Sometimes, one drive would not be able to read a disc, but then one of the other two drives would stil read it. I couldn't figure out if there was a relation between the drive that had been used to burn the discs versus the drive used to read them. Could be head alignment, could be simply incompability.
 

Crashes

Though Windows 7 is fairly stable, I've managed to crash the CD / DVD device drivers more than once. The PC was still working, but sometimes, when reading a (failing) disc, the specific drive would become locked up and would no longer be accessible to Windows 7 until the next reboot.
 

Storage conditions

Note: most of these discs have been stored in a living room for up to 10 years, followed by up to 7 years in the attic, including some 35+ degrees summers, wet and dry weather, and some soft winters (I guess the attick dropped to around zero degrees Celsius but probably not below).
 

Results

The table below lists brand, year, and success versus fail numbers. All cases where I could recover ALL files (even if I had to move the disc from drive to drive to get all files) I counted as successes. All discs where I could NOT recover ALL files I considered fails.

Most discs were the cheapest I could find, burned in 2003 and 2004, and read about ten to fifteen years later (I've been restoring stuff from 2012 to 2017). I haven't seperated CD's and DVD's, as over time CD's were phased out and replaced by DVD's.

DVD's have a worse track record than CD's. As some of those contained movies and were handled by my kids that doesn't necessarily indicate DVD's are by definition worse over time (though I suspect they are, or are at least more sensitive to damage). The majority of these disks have seen little to no use. Almost all failures in the table below were DVD's. 2 of the failed discs clearly had physical damage.

The LifeTec CD's all worked fine, but the reflective layer was becoming brown and transparent. Not a good sign...
 
Brand 2002 2003 2004 2005 2006 2007 2008
Nobrand / printable - 7 / 1 6 / 2 - 1 / 0 -
Nobrand / non-printable 2 / 0 3 / 0 2 / 0 1 / 0 - - -
Aterra Media - 3 /0 2 / 0 1 / 0 - - -
Bruna - 2 /0 - - - - -
Double Diamond Digital - 2 / 0 3 / 0 -
Getcopy - 3 / 0 - - -
Imation 2 / 0 4 / 0 7 / 0 1 / 0 - -
Lenco - 4 / 0 - - - - -
Lifetec 5 / 0 33 / 0 8 / 0 - - 1 / 0
Maxell - 3 / 0 1 / 0 1 / 0 5 / 0 -
Memorex - - 2 / 0 - 3 / 0 - -
Mmore - 34 / 1 20 / 1 1 / 0 - -
Nashua - - - 2 / 0 - - -
Octron - 11 / 0 6 / 1 -
Philips - - - 4 / 0 - 2 / 0 -
Platinum Plus - 1 / 0 14 / 1 -
Precision 1 / 0 2 / 0 2 / 0 - - - -
Pleomax (Samsung) - - - 2 / 0 - 5 / 0 1 / 0
Samsung (non-Pleomax) - 6 / 0 6 / 0 2 / 1 -
TDK - 1 / 0 1 / 0 - - - -
That's Wite - - - - - 1 / 0 -
Thing Xtra - 16 / 0 9 / 0 - - - -
Verbatim - 8 / 0 - -

Conclusion

This is obviously not the most scientific test :-)

1. Average failure rate of about 4%.
2. Age and storage time did not seem to matter much.
3. No brands that stood out, though 'printable' discs were worse than anything else.