[HN Gopher] The Reliability of Optical Disks
___________________________________________________________________
The Reliability of Optical Disks
Author : gandalfff
Score : 103 points
Date : 2022-04-02 15:25 UTC (7 hours ago)
(HTM) web link (blog.ligos.net)
(TXT) w3m dump (blog.ligos.net)
| btrettel wrote:
| > What I didn't realise at the time, was that all these CDs and
| DVDs would become a grand experiment of reliability and
| longevity. When I read data from these backup disks in 2021, I
| had a 100% success rate!
|
| My own experience is pretty good, but not 100%. I burned a lot of
| CDs from 2001 to 2006 or so. Most were discarded at some point,
| but in late 2019 I ripped all that I had (39 CDs) with (GNU)
| ddrescue. The vast majority (77%) had some small amount of read
| errors. I was able to recover 99.88% on the worst disk (a brand
| I'm not familiar with: "D"). That disk was about 15 years old.
| That's pretty good, but not 100%.
|
| This experience underlined to me the importance of having parity
| files in addition to the disks themselves. When I do a Blu-ray
| backup now (roughly once a year for the most important files), I
| also burn a DVD with par2 files.
|
| Back in the 00s I didn't verify checksums, but as a test I
| checked zip, gz, and png files on the oldest disk I had (Jan.
| 2001, 100% recovered). Those files have internal checksums to
| detect corruption. All those files passed. I should probably
| perform the same check on the other disks.
|
| Edit: I ran my script to check internal checksums on my disk
| image for my worst disk and 19 out of 635 files tested were
| corrupt, all png files. That is worse than the recovery
| percentage that ddrescue reports (97.01% valid vs. 99.88%
| recovered). That's roughly 0.2% lost per year.
| uniqueuid wrote:
| 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
| btrettel wrote:
| 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.
| uniqueuid wrote:
| 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!
| wtetzner wrote:
| 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.
| btrettel wrote:
| I don't know how likely some sort of electromagnetic event
| is. I just figure that if I'm going to diversify my backup
| strategies then something dissimilar/uncorrelated would
| probably be a better choice. My data is on magnetic hard
| drives, SSDs, and optical disks, each of which has
| different risk profiles.
|
| As wtetzner said, it's unlikely that a single event could
| cause all of these to fail. An EMP attack might take out my
| magnetic hard drives and SSDs but leave the optical disks
| unaffected. I've also had a hard drive fail due to impact
| damage that likely would not affect a SSD. Flooding is not
| something I've thought about before, but since my backups
| are located in different geographical areas, I should be
| covered there. Etc.
| axiolite wrote:
| > local electromagnetic event then I'd prefer to have a
| backup that can handle that.
|
| First of all, the magnetic gauss needed to flip bits on LTO
| media is huge. It's not a practical concern unless you're
| choosing an incredibly inappropriate storage location.
|
| Second, why wouldn't you store your tapes in a case or a
| vault that is magnetically shielded?
|
| You probably store your discs in cases, instead of insisting
| they be naturally durable against rough handling and
| abrasion.
| btrettel wrote:
| > First of all, the magnetic gauss needed to flip bits on
| LTO media is huge. It's not a practical concern unless
| you're choosing an incredibly inappropriate storage
| location.
|
| You're right, it does seem huge:
| https://superuser.com/a/568367/111650
|
| (Some of the links from this answer are quite interesting.)
|
| The issue is that I don't know (and I suspect it's
| difficult to know or even classified) whether an EMP attack
| (the main scenario I'm worried about, which can be quite
| powerful) would be sufficient to cause damage. I don't
| believe there is a consensus on this though I'd be glad to
| be proved wrong here.
|
| > why wouldn't you store your tapes in a case or a vault
| that is magnetically shielded?
|
| I would; as I said I put some magnetic hard drives in
| Faraday cages. However, I'm not confident that the Faraday
| cage would be sufficient. A lot of the discussion online
| about constructing Faraday cages to protect electronics is
| speculation. I haven't seen any clear data showing that
| during an EMP attack magnetic data is protected inside of a
| Faraday cage, or protected without one.
| axiolite wrote:
| > I'm not confident that the Faraday cage would be
| sufficient.
|
| Faraday cages are not intended for that purpose.
|
| Magnetic shielding is a well understood concept. What you
| need is some thickness of ferrous metals.
|
| https://en.wikipedia.org/wiki/Electromagnetic_shielding#M
| agn...
|
| https://web.archive.org/web/20070327130322/https://advanc
| ema...
|
| https://interferencetechnology.com/magnetic-shielding-
| basics...
|
| It's easy to test the efficacy of magnetic shielding
| yourself if you have a large, powerful magnet and a CRT
| monitor handy.
| btrettel wrote:
| Noted, thank you much.
| ndiddy wrote:
| 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 drive can
| read a CD-R from the 90s so this is less of an issue.
| uniqueuid wrote:
| 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!
| KennyBlanken wrote:
| 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 he got around to
| checking it)...
|
| ...no organization looks at a requirement like "archive these
| records for 50 years" and then commands its IT department to only
| store the data on media that will be expected to survive 50
| years.
|
| What you do is store the data in such a way that your chance of
| losing data per year is within acceptable margins, on the most
| suitable storage method at the time, _and migrated periodically
| when that system 's chance of data loss falls below acceptable
| margins, appears to be getting too impractical to
| operate/maintain, or there are improvements in reliability or
| practicality._
|
| That can include factors like cost, availability of knowledgeable
| labor (ask the IRS how finding COBOL programmers is going),
| parts/service availability/cost, and so on.
|
| Other comments:
|
| > HDDs, especially NAS disks, have an "always on" assumption
|
| Even in the early 2000's, commercial NASes were offering systems
| that could power down portions of the array that were unused.
| There was significant interest in minimizing opex, and that's
| mostly power. Nowadays unraid and other solutions allow for the
| same.
|
| > And if you ever wanted to take disks offline and store them on
| a shelf, you don't really know how long they'll survive - unless
| you plug them in every now and then.
|
| "you don't know if that HDD is gonna work if it's sitting on a
| shelf" is irrelevant _because your backups shouldn 't be sitting
| on a shelf for any significant period of time, regardless of the
| media/mechanism_. See discussion above: you should be rotating
| your media off-site periodically, bringing it back for tests. The
| biggest problem with HDDs is that SATA connectors are not rated
| for frequent use; their connect/disconnect rating is often in the
| range of "hundred or so." (This can be partially addressed by
| using a cable that stays plugged into the drive, and replacing
| the cable when it is past a certain number of cycles.)
|
| > if you ever wanted to take disks offline and store them on a
| shelf, you don't really know how long they'll survive - unless
| you plug them in every now and then.
|
| > And yet, the expectation is, that you will be able to read the
| disks without problem - even with zero maintenance. Indeed, that
| was the outcome of my ~15 year experiment!
|
| That's not the expectation, at all? CD-Rs used to have a lifetime
| measured in months before they start showing failures, especially
| if they had an adhesive label. I don't understand how the author
| possibly could be reading ten year old CD-Rs. That's basically
| impossible.
|
| DVD-Rs faired a bit better, and bluray disks even better.
|
| The issue with HDDs is the lubrication of the motor
|
| > any NAS will automatically check for errors, and notify if
| problems are found.
|
| No. No. No. NO. This is probably one of the biggest myths of RAID
| and NAS devices.
|
| Just because you have a RAID array doesn't mean it is configured
| to scrub its arrays; this often has to be enabled.
|
| Just because you have a RAID array scrubbing doesn't mean you're
| going to find out about it. Make sure your reporting works, and
| ideally report on success, not just failure, and have something
| else that reports on failure to receive
|
| Last but not least:
|
| Just because your RAID array controller (or software) finds a
| parity error or unreadable block doesn't mean it does what you
| expect, and most people expect "beep bop boop, parity/mirror
| inconsistency detected. Fixed, meatsack! Pat yourself on the back
| for being smart in using RAID."
|
| Reality: "beep bop boop, parity or mirror inconsistency detected,
| so go and verify your files or restore from backup, meatsack."
|
| RAID arrays cannot self-repair mirror or parity errors _because
| there is no way to do so._ The array controller has no idea
| whether it 's the parity bit that is wrong, or the data. In a
| mirror, it has no idea which drive is correct - just that one of
| them is bad. _RAID is not for data consistency._
|
| This is why ZFS is usually the top pick for data consistency: it
| knows the checksum of files and metadata, in addition to the on-
| disk redundancy via mirrored copies or parity. If it finds an
| error, it can play out both scenarios to see which results in
| files or metadata that match their checksum.
| gjs278 wrote:
| kevin_thibedeau wrote:
| > I don't understand how the author possibly could be reading
| ten year old CD-Rs.
|
| The cyanine dye CD-Rs were the most unreliable but the later
| phthalocyanine and azo discs are more robust. Mine all readback
| fine so long as they have been stored well without sunlight
| exposure.
| uniqueuid wrote:
| 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.
| WalterBright wrote:
| I buy multi-terabyte drives when they go on sale (which is often)
| and copy everything forward once a year or so. I don't trust old
| media of any sort.
| digisign wrote:
| Interesting because hard disks are not a particularly reliable
| form of backup. As long as you have enough copies.
| WalterBright wrote:
| I know, I've had many fail on me over the years. Quantity,
| though, has a quality all its own!
| lostmsu wrote:
| Same here. I just have a mirrored Storage Space for
| critical data with ReFS and checksums (though Microsoft did
| not make that one easy to understand so I am unsure if the
| data is safe that way).
|
| UPD. just searched, and found, that I needed to enable
| periodic scrubbing in Task Scheduler: Microsoft -> Windows
| -> Data Integrity Scan section. I already had data
| integrity streams enabled (another thing you have to do
| manually after creating the volume).
| gandalfff wrote:
| My biggest concern with Optical Disks is obsolescence and
| convenience. I bought some DVD media to do some backups but so
| far I have only backed up a portion of my photos. Right now my
| files are being stored on my MacBook's internal SSD, Backblaze,
| Google Drive, and a Time Machine backup on an SD card that stays
| in the SD slot. I do full backups to external hard drives every
| so often. I'm too lazy for any backup method that requires an
| involved process like optical media. And I also find myself
| asking if it's even worth it. I don't think my files are that
| valuable, to be honest. I would be sad to lose them, but it might
| also be freeing in a minimalist sort of way.
| kevin_thibedeau wrote:
| This misses the most reliable optical media which is DVD M-disc.
| password4321 wrote:
| No longer manufactured, I believe; only available on eBay?
| kevin_thibedeau wrote:
| It is still made.
| bufferoverflow wrote:
| I have many degraded CDs and DVDs from 2000-2010. No drive would
| read them. Most from reputable brands. Most non-RW. All stored in
| dark places, indoors.
| dylan604 wrote:
| Did you enable the "Try Really Hard" option? Can't remember the
| name of the software with it. Nero, maybe?
| btrettel wrote:
| Many disk imaging programs have similar features. I'm partial
| to GNU ddrescue.
|
| https://en.wikipedia.org/wiki/Ddrescue
| dylan604 wrote:
| 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?
| otterley wrote:
| The article focuses on Blu-Ray media, which has different
| physical characteristics than CD-R and DVD.
| agumonkey wrote:
| Interesting, I was surprised to be able to read medium or low
| quality brands from 99 well into 2010s. And I took no precious
| care.
| mjhagen wrote:
| I have a couple CD-Rs (from the early 2000s) that have
| completely lost their top layer. I suspect the cause is the
| label sticker that was used. But in any case, it's completely
| unreadable.
| HNHatesUsers wrote:
| superkuh wrote:
| I have many degraded CDs from 1998-2010. In 2019 almost all of
| them would read, eventually, even as metal flakes came off the
| disks. I recovered most data from most. My CD-Rs were a mix of
| brands, nothing special or expensive. But my CD-drives are old
| too, from 2006(?) or so. I wonder if like with floppy disks and
| drives, modern CD drives are less capable than old ones because
| they're no longer a premium product?
| girishso wrote:
| How did you recover the data from CD/DVDs? I checked at a
| local shop they are not interested in recovering CDs.
| btrettel wrote:
| > I wonder if like with floppy disks and drives, modern CD
| drives are less capable than old ones because they're no
| longer a premium product?
|
| When I ripped CDs I had from the 00s in 2019, I used an
| external Blu-ray drive from probably 2018 or so. Seemed to
| work okay; see [0]. I didn't have access to anything older so
| I can't compare but I think both new and old drives are
| probably good.
|
| [0] https://news.ycombinator.com/item?id=30889474
| robocat wrote:
| Blu-ray discs use a red laser, and CD-ROMs use an infrared
| laser. The drives contain two laser diodes. Skip to 5:50 in
| https://www.youtube.com/watch?v=h9lbrr04XBQ
| neuralRiot wrote:
| Blu-ray uses blue laser (blue-ray!) DVD uses red and CD
| infrared. Devices compatibles with the 3 mediums have 3
| lasers on their optical pickup.
| gjsman-1000 wrote:
| In my movie collection, I replaced almost every DVD I could with
| Blu-Ray. Not just because the quality is better - it was, as the
| author mentioned, the massively improved scratch resistance. When
| you have kids, it becomes cheaper in the long run.
|
| Also, we're a quality over quantity family. We don't want
| thousands of movies on several subscriptions. Everything we've
| ever liked fits on two four-foot-wide shelves.
| causality0 wrote:
| _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 more
| expensive to deter piracy or Sony's desire for high profit
| margins on data storage? I well remember Sony's shenanigans from
| the 2000s when they made great hardware and then only accepted
| MemoryStick instead of SD cards while charging much more for
| their flash format. I was so excited for BluRay and then prices
| just never came down enough to be practical.
| 29083011397778 wrote:
| 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/
| causality0 wrote:
| It's bizarre to me that lawmakers can get away with
| corruption that blatant.
| spansoa wrote:
| Worth looking into Millennium Disc or M-DISC[0]. Apparently it's
| media that can last 1000 years. Thinking of buying two 50GB disks
| and putting some backup files on them when I have a few coins to
| drop.
|
| [0] https://en.wikipedia.org/wiki/M-DISC
| oskarpearson wrote:
| The article covers m-disc extensively, not sure why you're
| linking Wikipedia here?
| hlieberman wrote:
| The author explicitly notes that he is testing M-Discs; in
| fact, for heat, he only tests M-Discs.
| kevin_thibedeau wrote:
| BD M-disc is the same as a normal BD-R. The DVD M-disc is the
| only one worth considering for long time archival storage.
| Wowfunhappy wrote:
| What makes you say that? The article appeared to find a
| significant difference in the reliability of standard BD-R's
| and M-Disc BD-R's.
| dsego wrote:
| There are two types of BD-Rs, high to low & low to high.
| One is bad for long term and one is good (something
| something inorganic), but I forget which is which. From my
| research online bluray m-disc is just the better one but
| m-disc branded, apparently not the same stuff as the
| original m-disc DVD.
| digisign wrote:
| Would concur. I went thru all my old optical discs in ~2020 and
| moved all backups to 100GB Bluray. Went from dozens of discs to
| about three. Then I destroyed most of the old ones. (Didn't
| bother with some... does anyone need a copy of Netware 3.x or 4.x
| anymore? Even though it was so cool at the time.)
|
| All my CDs/DVDs burned from about '97 onwards were in perfect
| condition. I think one deteriorated, stuff I didn't care about
| given to me. I never bought super-cheap ones, maybe that helped.
|
| I did save a few "mix tape" discs from the era for nostalgia
| purposes. Imagine 15 of the best songs from different artists on
| ONE disc! It was a big kick to make your own CDs at the time...
| would blow people's minds, when you showed them. :-D
| mulmen wrote:
| At the turn of the century half of my personal CD collection
| was mix CDs from friends. Someone broke into my 25 year old
| Toyota and took the CD wallet, spare change and the car
| battery.
|
| That was 9 years ago but I still wish I had a backup of those
| mix CDs.
| TacticalCoder wrote:
| My CDs burned in 1998 still read totally fine. TFA and your
| comment is, I think, what shall eventually make me move to
| BluRay. Any model/brand of writer/discs to recommend? (Linux
| here FWIW)
|
| EDIT: btw ofc all my pressed audio CDs all work just fine. My
| car for whatever reason, although semi-recent, still has a CD
| reader and I was listening to some Ennio Morricone CD in the
| car 10 minutes ago!
| digisign wrote:
| For newer stuff, I have an ancient 5-7? years-old external LG
| BLuray/MDisc drive, and use Verbatim media. Can't speak to
| their longevity so definitively. They are working fine after
| three years. I also have a few TB external backup drive for
| additional-copy and rapid-access to the same data. I take an
| optical disc to a relative's house once a year.
|
| Multiple copies, multiple formats, multiple locations, is the
| key to back up.
| jbverschoor wrote:
| About a month ago I went trough all my CD/DVDs. Factory disks
| were all good. But burned disks, especially the later cheaper
| ones mostly were either in bad condition, or not even
| recognized as media.
| digisign wrote:
| Brand? Treatment?
|
| I just grabbed one from my DJ days: TDK dated 1997-01-01:
|
| https://imgur.com/a/I7fokrx
|
| Listening to it now. We are... family
| jbverschoor wrote:
| After '00, the market was flooded with cheap discs.. Most
| of the bad ones were those.
| digisign wrote:
| I see. My DVDs were also fine, but I did stick to known
| brands, if memory holds.
| amelius wrote:
| There are specialized companies who claim to be able to
| recover data from just about anything. Probably expensive,
| though.
| ghostly_s wrote:
| 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?
| blueflow wrote:
| 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.
| [deleted]
| codazoda wrote:
| 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.
| xupybd wrote:
| Some plastics can react with other plastics you have to be
| careful when storing long term in plastic bags for this
| reason. I'm not at all sure if this played a part in your
| CDs but it's possible.
| em3rgent0rdr wrote:
| 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.
| tenebrisalietum wrote:
| Use PAR2 files, like Usenet does.
| tambourine_man wrote:
| I had a different experience. A good fraction of the CD/DVDs
| burned 10-20 years ago won't read. At least not trivially.
| yeetsfromhellL2 wrote:
| RO media is great, especially when you're concerned about data
| integrity and may not completely trust a machine writing or
| verifying the media. Consider you're downloading sensitive data
| from the internet, or just writing sensitive data on an internet
| connected machine (maybe it's OS installation media, or important
| legal or financial docs, or you're a wall street or NSA
| whistleblower, or it's a Bitcoin key backup), and you're worried
| your machine may be compromised on account of it being connected
| to the internet; you may not want to stake the quality of the
| rest of your life on your computer not lying to you about file
| integrity.
|
| What do you do?
|
| Write it to RO media and take it to different computers to verify
| the checksum/signature. You don't need to worry about other
| machines, which are also potentially compromised, corrupting the
| data. You also don't have to worry about something like BadUSB,
| where the USB device's microprocessor firmware infects the host
| machine (or vice versa) before the data payload is even read.
| This means you can put the disk in your secure airgapped machine
| at home, even after it's been in the machine at the local
| library. You create a concensus of file integrity after reading
| and verifying the data across a range of machines.
|
| Obviously there are other attack vectors, but with the cost of
| these sorts of attacks (badUSB, or simply getting rooted) going
| down, the accessibility going up, and the potential rewards
| becoming more valuable and widespread, it's an attack vector to
| consider for important data.
| rascul wrote:
| It feels weird to me to call optical media disks instead of
| discs.
| chrisseaton wrote:
| It's American English / British English isn't it?
| Wowfunhappy wrote:
| Nope!
|
| Apple--of all companies--has a support article on this:
| https://support.apple.com/en-us/HT201697
| chrisseaton wrote:
| > Nope!
|
| https://en.m.wikipedia.org/wiki/Spelling_of_disc
|
| > the spelling disk is more popular in American English,
| while the spelling disc is more popular in British English
| rascul wrote:
| > In 1979, the Dutch company Philips, along with Sony,
| developed and trademarked the compact disc using the "c"
| spelling. The "c" spelling is now used consistently for
| optical media such as the compact disc and similar
| technologies.
| rascul wrote:
| 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.
| theandrewbailey wrote:
| 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.
| jonsen wrote:
| "(The spelling disk and disc are used interchangeably except
| where trademarks preclude one usage, e.g. the Compact Disc
| logo. The choice of a particular form is frequently historical,
| as in IBM's usage of the disk form beginning in 1956 with the
| "IBM 350 disk storage unit").":
|
| https://en.m.wikipedia.org/wiki/Disk_storage
| SnowHill9902 wrote:
| What do you people need to store so much for so long? Backups are
| rolled-over ever few days. Personal photos and videos?
| nayuki wrote:
| 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 that
| a head crash could wipe out good data.
|
| I'm extremely disappointed that the capacity of optical disc
| formats are essentially frozen, topping out at 100 or 128 GB for
| BD XL. They're definitely not keeping up with the continual
| increase in storage density and decreasing cost of hard disks and
| flash memory. Why are new formats not forthcoming? Where's my 300
| GB Archival Disc? Where's my 1 TB holographic disc? Where's
| Microsoft's glass optical disc that's stable for millions of
| years?
|
| I want to keep on burning optical discs and putting them in cold
| storage, but this gradually obsolete technology is not making a
| convincing case for me today.
|
| Previously: https://news.ycombinator.com/item?id=26038893 ,
| https://news.ycombinator.com/item?id=29221418
| tinus_hn wrote:
| 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.
| smackeyacky wrote:
| Even lowly LTO2 is 400gb. Plus the reliability of long term
| storage of tape is much better researched.
| em3rgent0rdr wrote:
| 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.
| tinus_hn wrote:
| It is not known what the durability is for an optical disc
| format that does not exist. There is no optical disc format
| that stores the required amount of data.
|
| LTO tapes do store the required amount of data and if you
| want them to last extremely long you should make new copies
| every 10 years or so. Just like you should for optical
| media. Sure, some discs might last 50 years. But some
| others won't be readable after 15.
| hlieberman wrote:
| 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 studies, and has exemplars that have
| survived more than 150 years.
|
| Ink on paper, on the other hand, we have exemplars that are
| almost 1000 year old, with ink on vellum more than 2000 years
| old. It requires no tools whatsoever to read, and we have been
| working and understanding how it is best preserved for hundreds
| of years.
| TacticalCoder wrote:
| I've got a printed book from 1575 here. Some pages at the
| beginning are in a bad shape but otherwise everything is still
| perfectly readable. I don't know which type of paper/ink it's
| using though. It's some book about plants: apparently one of
| the most printed book (after the bible) back in its days.
| simonebrunozzi wrote:
| How would you "print" your backup on a microfilm?
| formerly_proven wrote:
| Lasers, just like normal film prints.
| tablespoon wrote:
| > How would you "print" your backup on a microfilm?
|
| There are services that can do that for you. You send them
| document images, they send microfilm back. I've never
| actually done it, but I've considered it, an I had this
| random service in my bookmarks: https://overnight-
| scanning.eu/microfilming-service/
| gotaquestion wrote:
| I have 5-1/4" floppies the early 80's that still read fine. I
| wonder if 3.5" floppies from 1995 would still work. I have a
| feeling the media was made more robustly in the early 80's
| because the sensors weren't that precise, so bits were written
| with way more field than they needed. Maybe in the 90's when so
| many bits were crammed on to the 3.5" that they weren't written
| as strong?
|
| Perhaps the same is true of optical media. Are higher density
| optical disks from later in the era less robust than earlier
| tech.
|
| Like the way Hobart mixers from the early 1900's are built like
| tanks and can outlast ones built today to save money.
| TacticalCoder wrote:
| During the first lockdown I dug out my old Commodore 128 and
| quite a few discs were still reading fine... But not all of
| them. I don't remember the ratio but I'd say about 2/3rd were
| still working.
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