Optical Media Durability (2020) | Hacker News Reader

Optical Media Durability (2020)

blog.dshr.org

35 pointswalterbell14 comments

The author's most recent update, from 2023: https://blog.dshr.org/2023/08/optical-media-durability-updat...

> 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.

I appreciate the level of attention to this problem.

I still do backups of my online storage to Blu-ray on occasion. You can get 25GB, 50GB, or 100GB discs, and it’s great insurance in case anything happens to Google Drive or whatnot… like last week…

Flash drives are cool too, but Blu-ray Discs will never have an accidental folder deletion or any temptation to be used as more than an archive…

Is your can stomach the upfront costs a tape drive is even better - tape has a much better durability record, but man are recent tape drives expensive.

My understanding, though, is that you have to keep them at room temperature? (I recall a suggested rule of thumb for LTO is 60-90 degrees – most certainly wardrobe or basement media, rather than storage unit media.)

The author has had better success than I have. Earlier this year I archived a couple dozen CD-R and DVD-R discs with mixed results. Most remained accessible, but a few were no longer readable, tested across multiple drives. In my case, the discs were cheap, CompUSA branded discs. Media quality certainly matters. These discs were also older than the author's, approaching 20+ years.

I tried loading some of my old burned CD-Rs a few years back and had very little success too. They were maybe 10-12 years old at the time. It was kind of sad.

I had a number of burned CDs flake out on me over the years.

I’ve often wondered if writing on a CD/DVD with a Sharpie had an effect on the reflective layer, as I remember back in the day there were special markers for writing on these disks. Like the author though, I have perfectly serviceable optical media in some cases over 20 years old so perhaps those pens were just another attempt to sell me something I didn’t know I didn’t need!

DVDs have the optical layer sandwiched between two layers of plastic, while a CD is only one layer of plastic with the optical layer coating the other side.. So a sharpie should be fine on a DVD, but might be problematic on a CD

I wish someone was doing similar tracking for M-DISC Blu Ray discs but perhaps they are too new to really test yet (other than accelerated aging).

Blu-ray M-DISC has been available since 2013, I believe. One article from 2013 mentioning Blu-ray in the context of M-DISC: https://www.zdnet.com/article/torture-testing-the-1000-year-...

So, 10 years would be a good starting point, but probably on the short side of things.

Is anyone doing this kind of research on SD cards?

I'm more interested in reads than exhausting the write cycles. I wonder what the "half-life" of each bit/byte is: years? centuries? And how much better are DVDs, fx.

I've never had a Blu-Ray fail on me, for what it's worth.

Research? I'm not.

Physics? I can tell you it's far from permanent. You have charge stored surrounded by insulator. You quantum tunnel it in. Over time, it leaks out. Anecdotally, I've had plenty fail. All else being equal, higher-density devices should fail more quickly in theory (but practice is often different from theory, and all else is rarely equal).

Sorry.

Upside: Periodically reading / re-writing should reset all the ones to ones and all the zeros to zeros.

What I've always wanted was a hundred slot SD/CF card reader, which could access them all at once.

Had anyone here used M-disc? I think this is probably the best solution for me, but I feel it is a bit if painting myself into a corner

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