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Up To 10% of CD-Rs Fail Within a Few Years
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?"
Exactly, in my own experience, I started using CD-Rs in 1996. Back in 2007, I spent the time to copy all my old CD-ROMs of value to a hard drive for archival. I found that pretty much all of them were readable, even the 5 or 6 that were from '96. The only one I had problems with was a hybrid audio/data disc that I foolishly wrote in a proprietary format. But 80 or so of the discs that were spread across all the years worked ok. I was actually surprised because I expected some to be unreadable. I do think its great that they are trying to improve the longevity of the discs though, but they should find a solution that doesn't require a special drive.
dvdisaster 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.
Mam-a is not what it used to be.
Buy Taiyo Yuden or Falcon.
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
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.
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.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
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.
John
You're right; sorry. Try this one: http://www.itl.nist.gov/iad/894.05/docs/CDandDVDCareandHandlingGuide.pdf, looking at pages 21-22. Also see the notes about adhesive labels on page 23. They're also a no-no. Pat
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 to check the CD/DVD, which is free, and if I get a bad one I use Elprime Media Recovery 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.
ACs don't waste your time replying, your posts are never seen by me.
Are they data or audio? Because if they are data you can use Elprime Media Recovery 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.
ACs don't waste your time replying, your posts are never seen by me.
If you have not tested your backup system, you do not have a backup system.
Go green: turn off your refrigerator.