[RndTbl] Optical media longevity warning
Hartmut W Sager
hwsager at marityme.net
Sat Oct 23 22:30:58 CDT 2021
This topic is very important (for longevity of your data), but both the original post and the follow-up tweets aren't very informative.
For starters, as the author Keith Kaisershot posted, he himself buys "cheap knockoff brand" (in addition to some Sony discs). El-cheapo deserves to lose his data.
Furthermore, the following 3 points never came up:
1. CD-R/DVD-R and CD-RW/DVD-RW are lumped together, even though they are day-and-night different for longevity, and even for immediate readability. CD-RW/DVD-RW has a much lower contrast between 0's and 1's than CD-R/DVD-R has. As such, for example, music written to CD-RW/DVD-RW tends not to play in boomboxes that don't specifically mention it, whereas CD-R/DVD-R will quite often play successfully in boomboxes that don't even mention CD-R/DVD-R, let alone CD-RW/DVD-RW.
2. Most brands of CD-R/DVD-R use vegetable dyes in the data layer, with a life quoted at 2-3 years. These vegetable dyes are similar to the indo-aniline and azo-methine vegetable dyes used in classic colour slide film, colour negative film, and colour prints, all of which fade over time, and faster if exposed to heat or light. (Kodachrome was much better than the rest.) Only Ciba-Geigy made light-fast print material using pure azo dyes.
3. Verbatim DataLife CD-R/DVD-R discs are radically different, using some kind of polymer in the data layer, and quoting 100 years of data life in good storage conditions. That's what I used exclusively back then, and it piqued my interest enough to do an experiment. I taped a Verbatim DataLife CD-R filled with data onto a south-side window, no curtain, directly exposed to sunlight for about a year. To my pleasant surprise, the whole disc was re-read perfectly on my computer!!
I also once dabbled with magneto-optical discs (great stuff!), but that's another story.
It was pointed out that, longevity aside, you need compatible reading hardware later to read the discs. For both reasons, I re-write (copy to elsewhere) everything every 2-3 years. I no longer use CD-R/DVD-R for backup (despite #3 above) because of the inconvenience. I now use 3 different clouds to immediately back up everything I "save", and once-in-a-while (after each scolding by some conspiracy-theorist), I write everything to a USB stick (where I also observe the 2-3 year re-write rule).
Oh, did I mention how deeply involved in photography I once was? :)
Hartmut W Sager - Tel +1-204-339-8331
On Sat, 23 Oct 2021 at 09:58, Adam Thompson <athompso at athompso.net> wrote:
Came across this, this morning: https://twitter.com/ablitter/status/1451278816924495878?t=QmhboC2T73DOhpaAgm8BVg&s=19
...so here's a periodic reminder that the centuries your optical discs were supposed to last? Let's call that *highly optimistic at best*.
I know several people reading this who back up to optical media, but only one (maybe two) who plan for media longevity.
Welp, there's your reminder.
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