The Reliability of Optical Disks • Hacker News Board

Re: The Reliability of Optical Disks

#31

Post by uniqueuid » Sat, Apr 02, 2022, 6:00 PM UTC

KennyBlanken wrote: post #6

Aside from the author dismissing tape because "drives are expensive" and then concluding that the primary disadvantage to optical is "the discs are expensive" (wow, big surprise...) and then he doesn't bother to actually calculate the costs of either... ...and not describing how they tested for errors... ...and not having particularly rigorous testing methodology (the DVD was apparently left for three months before h…

Small addendum: The default installs of OpenZFS automatically configure monthly scrubs (typically on the first Sunday of the month), which is a great thing.

Unfortunately, depending on your local mail setup and your user account setup, you won't get the mail that is sent on errors when it's delivered to the root account.

Re: The Reliability of Optical Disks

#32

Post by uniqueuid » Sat, Apr 02, 2022, 6:03 PM UTC

One option that hasn't been mentioned is tape archives. It's not for everyone, but tapes (LTO) do have a lot of technology and infrastructure behind them that is built for longevity.

In particular, you can do cost-efficient archives to multiple tapes and store them in safe locations. If (and that's a big if) the base cost of the drive is tolerable.

There was recently a wonderful post and discussion on LTO for "normal" nerds [1].

[1] https://news.ycombinator.com/item?id=30099540

Re: The Reliability of Optical Disks

#33

Post by theandrewbailey » Sat, Apr 02, 2022, 6:08 PM UTC

rascul wrote: post #18

chrisseaton wrote: post #10

Earlier quoted context omitted.

It's American English / British English isn't it?

Laser disc, compact disc, digital video disc, and blu-ray disc are (from what I understand) officially spelled with the c. I'm in the US and that is the typical way to spell it that I see, but I also see the k is generally used for hard disk and floppy disk. That said, there are a lot more instances of "disk" than "disc" used in the comments here so far.

The reasoning I've seen, is that disc is the recording media itself, whereas disk includes things like a sleeve, case, and/or IO heads.

Re: The Reliability of Optical Disks

#34

Post by btrettel » Sat, Apr 02, 2022, 6:10 PM UTC

uniqueuid wrote: post #32

One option that hasn't been mentioned is tape archives. It's not for everyone, but tapes (LTO) do have a lot of technology and infrastructure behind them that is built for longevity. In particular, you can do cost-efficient archives to multiple tapes and store them in safe locations. If (and that's a big if) the base cost of the drive is tolerable. There was recently a wonderful post and discussion on LTO for "normal…

One thing that keeps me from trying tapes is that they are still magnetic. If there's some sort of local electromagnetic event then I'd prefer to have a backup that can handle that. I keep some backup hard drives in metal boxes, which is probably enough (Faraday cage). However, optical disks can almost certainly survive a major electromagnetic event without special precautions.

Re: The Reliability of Optical Disks

#35

Post by simonebrunozzi » Sat, Apr 02, 2022, 6:11 PM UTC

hlieberman wrote: post #30

If I am looking at a ~100 years timescale for preservation of documents, there are exactly two choices that I would consider. At the hundreds of years timescale, exactly one. Those are, in order: 1. Microfilm/microfiche 2. Ink on 100% cotton paper, or ink on vellum The properties of microfilm have been well studied. It requires no technology other than a magnifying glass to read, has a well over 500 year lifespan in…

How would you "print" your backup on a microfilm?

Re: The Reliability of Optical Disks

#36

Post by uniqueuid » Sat, Apr 02, 2022, 6:13 PM UTC

btrettel wrote: post #34

uniqueuid wrote: post #32

One option that hasn't been mentioned is tape archives. It's not for everyone, but tapes (LTO) do have a lot of technology and infrastructure behind them that is built for longevity. In particular, you can do cost-efficient archives to multiple tapes and store them in safe locations. If (and that's a big if) the base cost of the drive is tolerable. There was recently a wonderful post and discussion on LTO for "normal…

One thing that keeps me from trying tapes is that they are still magnetic. If there's some sort of local electromagnetic event then I'd prefer to have a backup that can handle that. I keep some backup hard drives in metal boxes, which is probably enough (Faraday cage). However, optical disks can almost certainly survive a major electromagnetic event without special precautions.

Interesting. Is a magnetic event more plausible for you than other types of decay? I'd expect physical damage from something like a flooding to be much more likely than some sort of magnetic interference.

But that probably depends on the location you live in!

Re: The Reliability of Optical Disks

#37

Post by 29083011397778 » Sat, Apr 02, 2022, 6:14 PM UTC

causality0 wrote: post #16

Finally, optical disks are more expensive than HDDs - at least in cost per GB. A 4TB NAS branded HDD costs ~AU$160, which is ~4c/GB. My last BluRay purchase was for 3 x 50 spindles of 25GB disks costing AU$330, which works out to be ~9c/GB. For anybody with deep knowledge of the industry, is the price of discs an accurate reflection of costs or is it inflated by secondary factors such as attempts to make the media mo…

I thought BluRay was subject to the blank media levy in Australia, but apparently not! [0] Note that not every country got off without though - just a few lines down, the article notes the levy is present on BluRay discs in Finland, among others.

As an aside, I'm of the impression not enough people know about this levy. It feels to me like the kind of thing that fouls up the "nothing to hide" arguments regarding privacy; that is, a law few know about, but one that affects lots of people that wouldn't necessarily agree with being charged for something they may not be doing.

While I'm sure some people still pirate and rip to BluRay, I'd assume they're just as likely used for things such as home movies, format shifting (which is legal in Canada [1]), or just plain backups (which I use for important files like a keepass database or 2FA codes).

While this has drifted off-course slightly, it may at least have given you an answer regarding why BluRay discs didn't fall too far in price - at least if you're based in Finland.

[0] https://en.wikipedia.org/wiki/Private_copying_levy#Australia

[1] https://www.michaelgeist.ca/2012/11/c-11-impact/

Re: The Reliability of Optical Disks

#38

Post by wtetzner » Sat, Apr 02, 2022, 6:18 PM UTC

uniqueuid wrote: post #36

btrettel wrote: post #34

Earlier quoted context omitted.

One thing that keeps me from trying tapes is that they are still magnetic. If there's some sort of local electromagnetic event then I'd prefer to have a backup that can handle that. I keep some backup hard drives in metal boxes, which is probably enough (Faraday cage). However, optical disks can almost certainly survive a major electromagnetic event without special precautions.

Interesting. Is a magnetic event more plausible for you than other types of decay? I'd expect physical damage from something like a flooding to be much more likely than some sort of magnetic interference. But that probably depends on the location you live in!

I think the idea is just to have different kinds of backups that have different failure modes, to make losing everything at once less likely.

Re: The Reliability of Optical Disks

#39

Post by dylan604 » Sat, Apr 02, 2022, 6:25 PM UTC

btrettel wrote: post #28

dylan604 wrote: post #23

Earlier quoted context omitted.

Did you enable the "Try Really Hard" option? Can't remember the name of the software with it. Nero, maybe?

Many disk imaging programs have similar features. I'm partial to GNU ddrescue. https://en.wikipedia.org/wiki/Ddrescue

I understand that it was common thing to offer, but who literally called the feature "Try Reall Hard"?

The more I've been thinking about it, was it one of the audio rippers?

Re: The Reliability of Optical Disks

#40

Post by codazoda » Sat, Apr 02, 2022, 6:29 PM UTC

blueflow wrote: post #13

ghostly_s wrote: post #3

I'm a bit skeptical of these conclusions without more detail on the methodology. Does "100% success rate!" mean the author was able to mount the disks and read some files off them? Or did they actually have some method to verify check-sums of every file to identify bitrot?

It matches my experience. Even decades-old CD-ROMs only fail when they are scratched or physically damaged, which you can prevent by keeping them in appropriate cases and always put them back after use.

My own experience is different. I had several brands of CD media that lasted less than 10 years. Many of them you could see the damage (cracks through the shiny layer). Some were dark blue, some a light blue. Almost all of them were bad. I had them stored in a light proof zipper pouch and stored at room temperature in a closet. Maybe something special happened to them over the years but very few worked. This would have been some of the first CD-R and CD-RW media available. I opened them more than 20 years ago so the media would have been 30 to 40 years old today.

Anyway, I haven’t trusted optical since then.