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The Reliability of Optical Disks

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Re: The Reliability of Optical Disks

#91

Post by ximile »

nayuki wrote: post #74

Great article discussing the benefits of optical discs and the author's own experience of using them! I burned hundreds of discs a decade ago and read them all back perfectly, to my surprise. I strongly agree with the write-once behavior for photos and downloads. HDDs worry me in the long term because even if the platter holding the data is fine, the R/W head, mechanics, and electronics could fail, not to mention tha…

Higher capacity optical storage is under development (see https://foliophotonics.com/ for example). My guess is that it's just hard to beat tape or justify upgrading/modifying existing optical disk readers.

The selling point now isn't that is a temporary storage solution that happens to last long like CDs and DVDs. I'm sure you have to make a pretty good case to get a customer to switch their high reliability data storage to a novel format.

I do hope it can eventually come back though.

Re: The Reliability of Optical Disks

#92

Post by mrjin »

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?

I guess that was just an instance of the "Survivor Bias". I burnt hundreds of CD-R/DVD-R/DVD-RW disks from a various of vendors(mostly Sony, TDK, Verbatim, Kodak, maybe some other brands which I could not remember clearly, each brand should be at least 50 as I had always bought 50 pack tubes.) around 15 years ago and left them untouched for around 8 years when I needed to retrieve something from those archives. So I decided to check the health of those disks which was quite disappointing. I simply tried if I could read the first 10 disks in each tube and it turned out, for a brand, all 10 were not even able to be recognized. Other brands performed from 3, to 8 in 10 disks could be read. That was just simply trying to read, so the integrity of the contents were not checked at all. The only good thing was that I managed to locate what I was looking for and it was in RAR format which validates the hash when extracting, it was good. So I immediately tried to move those I wanted to keep to HDDs and the loss rate was over 50%, and for those recovered, I didn't have much confidence regarding their integrity neither as no checksums saved. So basically I wasted lots of time and money by choosing optical drives as archive media. In the mean time, all files I left on HDDs were perfectly fine. This might be another survivor bias too.

Re: The Reliability of Optical Disks

#93

Post by NavinF »

em3rgent0rdr wrote: post #78

Could do RAID 4/5/6 with Optical Disks too for additional paranoia. Ideally there should be some machine to go through old backups and upon first detection of an error, then it could regenerate the array from the remaining discs of that array.

That’s the biggest problem with optical disks. With no automation, it’s totally impractical for one person to maintain a full backup of everything they care about. 100TB is like 2000 discs plus parity.

Re: The Reliability of Optical Disks

#94

Post by lostgame »

Extremely lucky about this ‘100% success rate’.

After dealing with several valuable SEGA Saturn games that succumbed to bit rot, and are therefore worth practically nothing - (nor are they playable, obviously) - I backed up whatever optical disks I had left and have never used optical media since. I certainly never will again.

I just can’t trust it anymore as an investment.

I’ve got vinyl from the 50’s/60’s that still play great but after losing those SEGA games I just see those little plastic disks as ticking time bombs.

Re: The Reliability of Optical Disks

#95

Post by eezurr »

nayuki wrote: post #74

Great article discussing the benefits of optical discs and the author's own experience of using them! I burned hundreds of discs a decade ago and read them all back perfectly, to my surprise. I strongly agree with the write-once behavior for photos and downloads. HDDs worry me in the long term because even if the platter holding the data is fine, the R/W head, mechanics, and electronics could fail, not to mention tha…

Another issue I've had is bad blocks forming on my SSD drive. I thought I lost a bunch of photographs (nothing important thankfully, just amateur shots when I first got my hands on a camera), but searching around I discovered CHKDSK. 4 hours later and everything was back to normal.

My OS (Win10) is on the same SSD. When I made the decision to get a 1 TB SSD for the OS and media storage, deep down a voice whispered [dont do that]. That decision has come to haunt me 1 year (!) later. I used to use 128 or 256 GB SSDs for the OS and keep all my media on another HDD drive (which failed after 10 years).

Also: 1 TB discs:

https://techgeekforever.wordpress.com/2014/03/11/sony-and-pa...

Re: The Reliability of Optical Disks

#96

Post by eezurr »

Here's an older article on Disc Rot, for some counter points

https://www.vice.com/en/article/mg9pdv/the-hidden-phenomenon... [1]

https://www.howtogeek.com/682807/the-cds-you-burned-are-goin... [2]

[1] https://news.ycombinator.com/item?id=21668184

[2] https://news.ycombinator.com/item?id=23979241

Re: The Reliability of Optical Disks

#97

Post by the_af »

SnowHill9902 wrote: post #85

What do you people need to store so much for so long? Backups are rolled-over ever few days. Personal photos and videos?

Personal photos and videos indeed, I would guess. The one piece of data you can never get back or buy back if your only copy breaks down. Also, a kind of data that takes a lot of space, compared with, say, text documents.

Re: The Reliability of Optical Disks

#99

Post by PaulHoule »

em3rgent0rdr wrote: post #79
tinus_hn wrote: post #75

Earlier quoted context omitted.

How many people are buying these 128GB discs? Probably not a whole lot and that is the reason why nobody’s going to make the investment to create bigger discs. If you want huge local offline storage, the solution is tapes.

But it is already known that magnetic tape is much less reliable in long term storage. The author is looking for long-term reliability, not just huge local offline storage.

I remember seeing VHS tapes from the 1980s fail in the mid 1990s with the magnetic layer flaking off from the plastic tape.

Re: The Reliability of Optical Disks

#100

Post by PaulHoule »

uniqueuid wrote: post #47
ndiddy wrote: post #45

Earlier quoted context omitted.

IMO the biggest problem with tapes is getting data off of them. The LTO standard only has compatibility for 2 generations back (i.e. an LTO-6 drive can read LTO-5 and LTO-4 tapes, but nothing before then). This means that if you have data you want to store for 30 years, you will also need to factor in the difficulty of finding a working tape drive and a computer that can operate it. With optical media, a new Blu-Ray…

True. But on the flip side, the LTO spec guarantees that this two-generation backwards compatibility will remain for the forseeable future. As the article mentions, it's possible that optical discs will become unpopular and cease to exist completely. With tapes, you're in the same boat as a bucket full of institutions to whom archives are VERY important. That's a big plus!

The supply of new media for LTO hasn't been stable...

https://www.theregister.com/2019/05/31/lto_patent_case_hits_...

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