Thursday, August 17, 2023

Optical Media Durability Update

Five years ago I posted Optical Media Durability and discovered:
Surprisingly, I'm getting good data from CD-Rs more than 14 years old, and from DVD-Rs nearly 12 years old. Your mileage may vary.
Four years ago I repeated the mind-numbing process of feeding 45 disks through the reader and verifying their checksums. Three years ago I did it again, and then again two years ago, and then again a year ago.

It is time again for this annual chore, and yet again this year every single MD5 was successfully verified. Below the fold, the details.


MonthMediaGoodBadVendor
01/04CD-R5x0GQ
05/04CD-R5x0Memorex
02/06CD-R5x0GQ
11/06DVD-R5x0GQ
12/06DVD-R1x0GQ
01/07DVD-R4x0GQ
04/07DVD-R3x0GQ
05/07DVD-R2x0GQ
07/11DVD-R4x0Verbatim
08/11DVD-R1x0Verbatim
05/12DVD+R2x0Verbatim
06/12DVD+R3x0Verbatim
04/13DVD+R2x0Optimum
05/13DVD+R3x0Optimum
The fields in the table are as follows:
  • Month: The date marked on the media in Sharpie, and verified via the on-disk metadata.
  • Media: The type of media.
  • Good: The number of media with this type and date for which all MD5 checksums were correctly verified.
  • Bad: The number of media with this type and date for which any file failed MD5 verification.
  • Vendor: the vendor name on the media
The drives I use from ASUS and LG report read errors from the CDs but verify the MD5s correctly. I didn't notice them reporting any read errors from the DVDs. An off-brand drive fails to read the CDs, but read one of the older DVDs with no read errors.

Surprisingly, with no special storage precautions, generic low-cost media, and consumer drives, I'm getting good data from CD-Rs more than 19 years old, and from DVD-Rs nearly 17 years old. Your mileage may vary. Tune in again next year for another episode.

Last year I found a NetBSD1.2 CD dating from October 1996 whose cksum(1) checksums all verified correctly despite a few read errors. That CD was still delivering good data after nearly 26 years, but this year a couple of the checksums failed.

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