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...

Update: I found another batch of discs, and am in the process of adding the results to the table below.
 

Drives

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

- external USB Liteon eTAU108
- external USB MaxCube CD-SL07-U2S / Teac DC-W28S-R
- 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, I do not know.
 

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 wilst 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 some years in the attic, including some 35+ degrees summers, wet and dry weather, and several 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 the period 2002 to 2006. I haven't seperated CD's and DVD's, as over time CD's were phased out and replaced by DVD's. I have been trying to read them a number of years later, as marked in the header of the table below.

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.

The LifeTec CD's and Mmore CD's were mostly fine, but the reflective layer was becoming brown and transparent. Not a good sign...
Brand 16 yrs 15 yrs 14 yrs 13 yrs 12 yrs 11 yrs 10 yrs 9 yrs 8 yrs
Nobrand / printable - - 7 / 1 6 / 2 - 1 / 0 - -
Nobrand / non-printable - 2 / 0 3 / 0 2 / 0 4 / 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 5 / 0 8 / 0 7 / 0 1 / 0 - - -
Lenco - - 4 / 0 - - - - - -
Lifetec 5 / 0 7 / 0 33 / 0 8 / 0 - - 1 / 0 -
Maxell - - 3 / 0 2 / 0 1 / 0 5 / 0 - -
Memorex - - - 2 / 0 - 3 / 0 - - -
Mmore 2 / 0 - 34 / 1 20 / 1 1 / 0 - - -
Nashua - - - - 2 / 0 - - - -
Octron - - 11 / 0 6 / 1 2 / 0 - -
Philips - - - 2 / 0 4 / 0 - 2 / 0 - -
Platinum Plus - 3 / 0 2 / 0 14 / 1 - -
Precision - 2 / 0 2 / 0 2 / 0 - - - - -
Pleomax (Samsung) - - - - 2 / 0 - 5 / 0 1 / 0 -
Samsung (non-Pleomax) - - 6 / 0 6 / 0 2 / 1 - -
TDK - 2 / 0 1 / 0 1 / 0 - - - - -
That's Wite - - - - - - 1 / 0 - -
Thing Xtra - - 23 / 1 9 / 0 - - - - -
Verbatim - - 8 / 0 - - -

Conclusion

1. This is obviously not the most scientific test :-)
2. Average failure rate 2%.
3. Age and storage time did not seem to matter much... yet
4. Read speeds varied, but many disks would only read at slow speeds
5. No brands that stood out