Up To 10% of CD-Rs Fail Within a Few Years 317
Whatever you think about the likelihood that a new kind of DVDs could last for 1,000 years, this note from reader crazyeyes should give you pause about expecting current CD-Rs to be reliably readable for decades. TechARP found a failure rate near 10% for CD-Rs recorded 7 to 9 years ago, after storage in ideal conditions. On some, one or more individual files could not be recovered; others were not reliably readable on two separate drives. "In the past, hard disk drives were small (in capacity) and costly. To make up for the lack of affordable storage, many turned to CD-Rs. As it became common to store backups and personal pictures, videos, etc. on CD-Rs, the lifespan of these discs became a concern. According to manufacturers, CD-Rs should last for decades. Some even quoted an upper limit of 120 years based on accelerated aging tests! That sure is a long time, isn't it? But will CD-Rs really last that long?"
Re:i have entire 1993 CD-R spindle (Score:1, Informative)
The earlier burners were expensive and better quality so it's probably more of a burner issue than a disk issue in this case. I've had a lot of disks die after even a few years buy they were burned on consumer level burners. Multiple back ups and later storing on hard drives was my solution. I find the DVDs more stable though because I just yesterday pulled files off an eight year old DVD and they were fine.
Re:According to... (Score:5, Informative)
Old news (Score:4, Informative)
dvdisaster anyone? (Score:5, Informative)
dvdisaster [dvdisaster.net] is what I use now...both on CDs and DVDs (it also supports dual-layer)
think of it as a way to embed par2 (parity) onto a disc (it requires an ISO image that you create in your favorite authoring software, then after it's done embedding the parity in it, you can burn it)
alternately, you can create a separate recovery data which you can store on backup tapes or hard drives or on another disc, etc.
Re:Not sure that hard drives are any better... (Score:4, Informative)
"Fairly often"? On what timescale?
In the consumer market: We had ATA for something like twenty years. And now we have SATA, with no replacement in sight.
Before that, we (consumers) had MFM and RLL.
And that, sir, is the complete history of PC hard drive interfaces.
So, again: "Fairly often"?
Re:Buy Quality Blanks!!! (Score:4, Informative)
Mam-a is not what it used to be.
Buy Taiyo Yuden or Falcon.
Re:i have entire 1995 CD-R spindle (Score:3, Informative)
There's error correction on CDs, the problem is that a 'bad' burner could produce a disk which is correctable to the proper data, but later on as some material degrades, will become unreadable, as opposed to simply requiring some error correction.
There used to be some brands that the firmware would show stats of that, however there haven't for a number of years, barring a few firmware hacks. (Amusing having to hack the firmware to get information that used to be semi-common.)
how to get good burn quality (Score:5, Informative)
I burn thousands of CDs and DVDs per week and here are some tips
- use pro grade media from Taiyo Yuden (Made in Japan) or Falcon (Made in UAE). Verbatim still makes some good media but you have to know what to look for (Datalife Plus) because they also buy cheap media and rebrand it.
- burn cd-r at 16 or 24x. 32x is ok for short-term use. Even the best discs will fail if you burn at maximum speed.
- burn dvd-r at 8x
- if you must burn dvd-r at 16x, test your quality regularly for signs of failure.
how to test the quality:
- Plextor made good drives bundled with Plextools testing software but they are no longer making their own drives. For a replacement to Plextools, see Opti Drive Control at cdspeed2000.com
Re:Not sure that hard drives are any better... (Score:3, Informative)
Fortunately, Nissan doesn't make hard drives(*).
Of course, the grease in the bearings can dry out, but that really doesn't seem to be much of a problem: It's a silicone-based substance, and it's wrapped up pretty tightly away from the ambient environment. There just isn't much for it to do except sit around and be stable... Old drives used oilite (sintered bronze) ball bearings almost as a rule, while newer ones often use fluid dynamic bearings -- and in either case, that aspect is fairly stable.
I've recovered data from hard drives that have been submerged in flood water for four days. They're durable little creatures, for sure, but even then at least half of the drives I touched after that flood were impossible to recover with my (primitive) methods.
That said, the biggest problem seems to be stiction. The heads of a hard drive normally fly slightly above the surface of the disk in operation (courtesy of the Bernoulli effect), but typically rest on the platter itself when the drive is not spinning. If left there long enough, the (very flat) surface of the head sometimes sticks to the (very flat) surface of the disk.
Sometimes, a disk can be spun up normally after a few years; other times, the spindle motor will stall trying to unstick the heads. There's various methods to relieve this striction, such as freezing, baking, or spinning the drive by hand on a tabletop and letting momentum free the heads, but they're all ugly.
So: For long-term, offline storage, I stick to offline-oriented media. Tapes might be good, DVD/CD-R might be good (and the admonished DVD-RAM is almost certainly better). Hard drives? It almost sounds like a bad joke.
(*: Not to pick on Nissan, by any means -- it seems that automotive chemistry isn't always just straightforward. I just replaced the radiator expansion tank on my BMW, after it exploded with a shotgun-like blast of steamy coolant. BMW used bad plastics in the cooling systems of on all of their early E36 3-series cars, including the water pump, the radiator, the expansion tank, the cap, and the thermostat housing. The radiator was new in 2003, the water pump was also recent, and I assumed that the expansion tank was also new with the radiator. I assumed wrong. A couple of days later, the fill cap fell apart, and failed to contain pressure. Live and learn.
Re:i have entire 1993 CD-R spindle (Score:5, Informative)
The earlier burners were expensive and better quality so it's probably more of a burner issue than a disk issue in this case.
Not likely, burners do not affect the aging of disks. It is the dye on the Aluminum that ages and eventually kills the disk - typically a result of oxidization. Cheaper disks use cheaper dyes. The brand name disks are more expensive because they use dyes that are patented - and therefor more expensive to license. The plastic coating that protects the dye from oxidization is also likely to be different on the more expensive disks.
Personally, I've only noticed flaws in the cheap disks - the brand name disks appear to age well. But the cheap disks are still very useful. I use then when distributing files to friends and family - this way I do not have to worry about getting them back.
4 CD, Raid 5. (Score:5, Informative)
I used-to make 2 CDs of every ISO, until I figured out how best to utilize PAR2.
PAR2 calculates parity information on a set of files, and writes out a file which can be used in the event that any of the files is damaged. This is quite similar to RAID-5, but PAR2 is more robust, and works on any files, not just equally sized hard drives.
Though it's no help on DVDs, CDs work GREAT with PAR2, because of their two different methods of recording. Mode 1, as all regular files are stored, reduces the amount of space available by about 12.5%, using that space for additional error correction data. Audio CDs, and Video CDs, where a single bit error isn't nearly as critical, are recorded in Mode 2, with substantially reduced error correction, but about 100MBs more usable space available.
PAR2 is similarly resilient to errors, so it can safely be used with Mode 2. This allows much more space for the parity information, and the opportunity to be safe against, and correct, respectively more damage to a disk.
Specifically, I recomend a 4-disk parity set. You fill 3 CDs full of data, and tell PAR2 to calculate 37% recovery data on those files. The first 33.334% allows you to RECOVER THE DATA FROM ONE COMPLETELY LOST CD, no matter which of the 3 it is. That still leaves you with a margin of 3.667%, so those two CDs you DO have, can have a few bad sectors as well, and all the data from the lost CD, as well as undamaged versions of the files on the two lightly damaged CDs can be recovered. Alternatively, if you DON'T lose an entire CD, all three (4 actually) CDs can have numerous bad sectors, in any distribution, up to a total of 37% of all the discs, and pristine data can still be recovered.
The method to do all this is quite simple. Just run the par2create command, telling it to create 37% recovery information. Then take the resulting BASENAME.Par2+??????? file, and create a CUE file, describing a CD with a single track across the whole CD, with the PAR2 file as the supposed audio data. eg.:
Now, any CD recording software that understands CUE files will happily record this to disc. On Unix systems, you can choose cdrecord, or cdrdao.
Now, like regular audio CDs and Video CDs, you can't just use or copy this data off the disc like a normal file on a CD. There are programs for converting VCDs into regular files, something like dat2mpeg, but I prefer a more generalized tool that can do the job:
mplayer vcd://2 -dumpstream -dumpfile par2.bin
You'll note that checksums of the file and the data on disk don't quite match... This is because, in mode2, data MUST be padded to the block size. PAR2 files are fine with it, and the padding is silently discarded.
Something like DD_RESCUE to copy the (normal) files off the other CDs, in the event of damage, is probably necessary as well. Then, once you've got 3CDs worth of data (eg. 700MB CDs x 3 = 2100MBytes) you can run par2recover and all with be repaired, like magic.
The only footnote being that calculating the parity information isn't fast, so this method is probably slower than just recording 2 copies of every CD. Also, if you lose more than 37% of the data across all the discs, the error-free originals can't be recovered. However, I consider it more reliable than duplicate discs, if only because the odds of an error on the same sector of two discs (or one disc lost, and the backup with a few errors), seems more likely than 37% of the discs being damaged beyond hope. And as an added bonus, you save 1/3rd on your CD-R purchases.
Re:Depends on the brand (Score:5, Informative)
By brand, you mean "manufacturer". Most big names, such as Sony, etc., don't make their own disks, but buy them from an external factory and place their own labels on them. The various manufacturers have different chemicals and dyes embedded in their discs, and its that chemical composition that determines the longevity.
Usually the brand will buy discs exclusively from one factory, but some of the off-brands (such as house-branded Office Depot or no-name discs at Micro Center) could be sourced from anywhere, and their quality will vary widely.
Re:Storage under "ideal conditions"... (Score:2, Informative)
cool dry place w/ no sunlight / UV. get a large CD storage folder (they usually have em for holding 500 or so disks and leave it in a drawer.
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So the quality got better! (Score:4, Informative)
(Throw a coin. If it's heads, read the P.S. first. Lucky you.)
I remember a large-scale test with pretty much all CD-Rs and CD-RWs on the market back in (around) 2000 (I think).
They used a climate chamber with all the effects of nature, amplified so much, that they could simulate 10 years of normal daylight, humidity, etc.
The blue and green materials died first. (I think blue was much worse than green, but only for some models.) After an average of 3-4 years! The original golden material survived better, but not much.
Only CD-RWs could even come close to 20 years, because they had to be manufactured better, and use other materials.
I also remember that our very first CD-Rs, burned on a huge rented SCSI burner, at 13 DM a piece, were unreadable right when we took them out of the archive one year later. Which was still better than those 50% who never survived the first burning at all.
Everyone around me always tells me that his old CD-Rs still work, and things like that. And they do not take me seriously when I tell them of the low life-span.
But usually, they do not even take them out to try them. And if they do, they look at the directory index, and think that means that all data is OK. And even than sometimes fails.
Also, they rarely can find CD-Rs, old enough to prove me right on the spot.
But if you take those discs, transfer everything and all its data to the hard disk, and then look at what you get, usually what you're left with, looks like a shattered mirror or the output of a random number generator.
P.S.: Sorry, just watched the Watchmen again (is that a pun?), and inadvertently wrote the whole comment in Rohrschach's journal voice.
Re:Depends on the brand (Score:3, Informative)
I recommend to always update your BIOS. From what I know, this gives the BIOS infos on how to read more recent discs (they are apparently not all equal, which makes sense).
I have to see it help though. Some readers are just shit. (Like my Samsung for DVD-RAMs [firmware crashes. hard.])
Re:My experiences with CD-Rs - some good, some not (Score:4, Informative)
Re:CD-Rs Design is Flawed. DVD-R More Reliable. (Score:2, Informative)
This is one of the reasons I argued that HD-DVD was a better choice versus Blu-Ray. But here on Slashdot, the moderators that had already invested in Blu-Ray always modded my posts down.
And now someone's going to be tempted to post about how the anti-scratch coating means that having the data layer on the bottom of the Blu-Ray disc means that there won't be any problems, and that I'm worrying for no reason. And I'll reply with the common sense answer that they always miss: it won't be a super-duper anti-scratch coating for much longer. You know they're just going to start slapping cheaper and cheaper anti-scratch coatings on those things. All they (and you, as a consumer) care about are cheaper prices, so who gives a crap about data longevity, right?
That exposed data layer and the inclusion of region codes again (just like with DVDs) were the two reasons that persuaded me that Blu-Ray was a worse choice compared with HD-DVD. But given that Blu-Ray won, it seems I'm one of the few people who cares about that sort of thing.
Enjoy your Blu-Ray discs, Sony fanboys. You've earned them.
Re:According to... (Score:5, Informative)
You can not only do that to ensure data, you can also use one of several free CD/DVD checking utilities and simply burn a new copy if the disc starts to go. I use DiskCheck [e-systems.ro] to check the CD/DVD, which is free, and if I get a bad one I use Elprime Media Recovery [elprime.com] which is not to recover it. With this combo I have been able to save discs that looked like my boys had used them for hockey pucks.
But I have several discs from the days of my $300 1x DVD burner, and several from the days of my 12x CD Burner, and they are still readable. I just run the oldest discs through DiskCheck once a year and if it reports any troubles I make a new copy and chunk the old one. But CDs are...what? Like $15 for a 100? And DVD is $20 for 100? So replacing the discs that start to go bad with age is no problem, and lets face it, when they are cranking out discs for that cheap bad batches are bound to slip through occasionally, and I have my old 8x DVD Burner installed in a 733MHz I use for Win9x so checking is simply a matter of feeding it while I switch back over with my KVM to check results. But with a simple yearly check you can get your data back by simply getting it off before the media degrades. And I have had a lot less problem with CD/DVDs that have been sitting in a dark cabinet for 5 years than I have with HDDs that have done the same. YMMV of course.
Re:According to... (Score:5, Informative)
Are they data or audio? Because if they are data you can use Elprime Media Recovery [elprime.com] to get most of the data back. It is $39 but you can see with the demo if it is gonna work with your discs or not, and how much it will recover. I have used it to get a good 85-90% back off of discs that looked like they had been used as hockey pucks, as well as for a couple where the dye had started to go.
So if you haven't tossed the discs you can probably get a good deal of your stuff back. And since you used buggered I assume you are British, which makes $39 USD...what? Like $2 in your currency? And while I can't say about CDs, as I haven't used them for anything but Linux liveCDs in ages, I can tell you there are a couple of DVD brands I would avoid like the clap. One is a bunch called Ilo, whose dye seems to go bad after about 9 months, and anything branded Staples. Do they have Staples in England? If so to quote the great Monty Python "RUN AWAY! RUN AWAY!" as I bought a couple of 50 packs there last Black Friday and a good 40% were coaster and the ones that burned correctly were in the garbage in less than 6 months due to bitrot. I have never seen a shittier brand in my life.
I have found Ridata to be the best of the cheapos as far as CD/DVD is concerned. I rarely get more than 5% coasters and have had no trouble reading 5 year old DVDs from them. And at $20 USD for a 100 from Newegg you just can't beat the price. You can also keep an eye on Surpluscomputers.com as they often get Taiyo Yuden CDs there cheap. Oh, and OT, but if anybody needs a server cheap Surpluscomputers has dual Xeon 3GHz HPs for $129. They'll even sell you a 10 pack of IBM dual Xeon 2.4GHz 1u for $599. Great place for when you need some hardware for cheap.
Re:Depends on the brand (Score:2, Informative)
It's not just the dye that determines longevity. I purchased a BUNCH of Verbatim CDR media 3 years ago. What I didn't realize is that the Verbatim discs do not have a plastic layer over the dye layer on the top. Only on the bottom. Recently I discovered that every single one of the 100 or so discs were useless because the dye layer simply peeled off of the plastic disc and took the data with it. Many of those files were not replaceable. I can't really call those my favorite brand these days.
Re:According to... (Score:4, Informative)
Re:Depends on the brand (Score:3, Informative)
Re:Depends on the brand (Score:3, Informative)
Yes, older Plextor drives are great for reading discs that other readers have problems with. I work at a company specializing in forensic software for optical media and we recommend the older Plextors to our customers and we always have a stockpile at our office. The older Plextor drives were built with much better optics and other components compared to the cheap stuff drives are made of today which is a major reason they read discs better. However, current Plextor drives are all rebadged drives from other manufacturers so I don't recommend those.
Re:4 CD, Raid 5. (Score:3, Informative)
Erm, that isn't Mode 2 records, that's audio data padded to 2352 byte blocks.
Mode 2 sectors have a sync header plus a (minutes/seconds/sector No/Mode No) for each block and have 2336 bytes for each block. White book (video CD) sectors have an additional XA header and a 4 byte checksum with a final data rate of 2324 bytes per sector (Mode 2/Form 2 sectors).
Re:According to... (Score:5, Informative)
If you have not tested your backup system, you do not have a backup system.
Re:According to... (Score:4, Informative)
It's not that simple. A number of brands are rebranded other brands. Taiyo Yuden is usually considered the best of the best.
For example, HP discs used to be Taiyo Yuden. But they have switched to something else now.
From personal experience... (Score:3, Informative)
Everything I was trying to open recently was about 7 years old, and about half the discs wouldn't even read, or would throw errors when I tried to actually copy anything off them.
It also opened up the issue of file formats...what the hell am I going to do with an Aldus Pagemaker file from 2001? Nothing in Adobe CS3 had any idea what to do with it. I think that's what that extension was, anyway. Archiving photos and videos is pretty safe as far as file formats go. A BMP is crappy and gigantic next to a TIFF or PNG, but you can still open it.
Proprietary layout formats though...they get old faster than cheese in a hot car.