Thursday, August 20, 2020

Optical Media Durability: Update

Two 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.
A year ago I repeated the mind-numbing process of feeding 45 disks through the reader and verifying their checksums. It is time again for this annual chore, and once again this year I failed to find any errors. Below the fold, the details.


MonthMediaGoodBadVendor
01/04CD-R50GQ
05/04CD-R50Memorex
02/06CD-R50GQ
11/06DVD-R50GQ
12/06DVD-R10GQ
01/07DVD-R40GQ
04/07DVD-R30GQ
05/07DVD-R20GQ
07/11DVD-R40Verbatim
08/11DVD-R10Verbatim
05/12DVD+R20Verbatim
06/12DVD+R30Verbatim
04/13DVD+R20Optimum
05/13DVD+R30Optimum
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
Surprisingly, with no special storage precautions, generic low-cost media, and consumer drives, I'm getting good data from CD-Rs more than 16 years old, and from DVD-Rs nearly 14 years old. Your mileage may vary. Tune in again next year for another episode.

One observation is that the Mint Linux system I used to check the CDs (and a few of the DVDs) currently runs kernel version 5.0.0-32-generic. Each of the CDs read perfectly, but as each was mounted the kernel logged the following error:

kernel: [  182.504692] sr 2:0:0:0: [sr0] tag#0 CDB: Read(10) 28 00 00 05 64 30 00 00 02 00 00 00
kernel: [  182.504699] print_req_error: critical target error, dev sr0, sector 1413312 flags 80700
kernel: [  183.315607] sr 2:0:0:0: [sr0] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
kernel: [  183.315613] sr 2:0:0:0: [sr0] tag#0 Sense Key : Illegal Request [current]
kernel: [  183.315616] sr 2:0:0:0: [sr0] tag#0 Add. Sense: Invalid field in parameter list
kernel: [  183.315621] sr 2:0:0:0: [sr0] tag#0 CDB: Read(10) 28 00 00 05 64 30 00 00 02 00 00 00
kernel: [  183.315624] print_req_error: critical target error, dev sr0, sector 1413312 flags 0
kernel: [  183.315632] Buffer I/O error on dev sr0, logical block 176664, async page read


4 comments:

Dorothea said...

Could you say a little bit more about the storage conditions? What's the temperature range on a "shirt-sleeve environment" and how's the humidity?

A few years back my students rescued linguistics data, about ten years old, from fifty or so CDs kept in an academic office whose windows didn't open (common on our campus). About 10% had already gone bad. Anecdata, but I am curious about environmental tells.

David. said...

The media are stored in their retail plastic 100-disk packages on a shelf in a closet in the laundry room of a non-air-conditioned house in Silicon Valley. Checksums were validated before storage, so they all started out known-good. They are all still good.

Jason Scott said...

Send them to me in your will, sir, and I'll continue the task in your honor.

David. said...

Thanks, Jason, you have a deal. They are now labeled "Send to Jason Scott @ Internet Archive"