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How To Verify CD-R Data Retention Over Time?

CmdrTaco posted more than 5 years ago | from the saving-boobies-for-future-generations dept.

Data Storage 303

Peter (Professor) Fo writes "I've recently had two CD-Rs reported to me as faulty which are just 3 years old. This is worrying — I suspect the failure rate for this batch could be 10%. When researching CD longevity there is old and unreliable information; pious 'how to cosset your discs so they last 100 years' blurb; and endless discussions of what sort of dye to use, don't use cheap media, burn slower (or don't), but not much by way of hard facts besides there's a lot of data loss going on. Does anyone know of a generic utility (win or *nix would suit me) that can map sector readability/error rates of CDs? I'd like to measure decay over time in my environment with my media and my other variables; and I expect others would too."

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303 comments

The tools are called (-1, Flamebait)

spazdor (902907) | more than 5 years ago | (#25662631)

dd and diff.

Re:The tools are called (4, Insightful)

tepples (727027) | more than 5 years ago | (#25662729)

dd and diff.

Those tools provide no signal-to-noise ratio (Block Error Ratio, BLER) for physical media errors that the drive is just barely correcting. The point of the request, as I understand it, is to detect how likely a correctable medium is to stay correctable.

Re:The tools are called (0)

Smidge207 (1278042) | more than 5 years ago | (#25663043)

Huh. I am in the way of understanding that if you print out MP3 files (i can haz Unicode, plz?) the S_n_R is nearly 100%.

Tip your waitress, try the lobster. Blah blah blah.

=Smidge=

Re:The tools are called (-1, Offtopic)

Anonymous Coward | more than 5 years ago | (#25663389)

To say that you've missed the point would be a massive understatement. You're the reason that we need a -2 mod.

Re:The tools are called (5, Informative)

digitalchinky (650880) | more than 5 years ago | (#25663125)

Short of an electron scanning microscope, the only way to do it is to hook an oscilloscope directly on to the test points within the drive itself and measure signal levels. This will allow you to measure one or both of: Degradation of the laser optics, degradation of the media. It's anyones guess as to which is which :-)

To make things a little more accurate, you should use several drives to test the media. The drives could benefit from being locked away until such a time as they are needed to repeat the tests. Mix in a few new drives when you do actually make your tests in future as well.

If drive makers were SMART, they would... (4, Insightful)

tepples (727027) | more than 5 years ago | (#25663323)

Short of an electron scanning microscope, the only way to do it is to hook an oscilloscope directly on to the test points within the drive itself and measure signal levels.

Or the manufacturer of an optical drive could do the SMART thing: provide some sort of self-monitoring, analysis, and reporting tool [wikipedia.org] to let the user see how many errors the drive has corrected per MiB of data. Mobile phones, Wi-Fi cards, and digital TV converter boxes do something like this, showing SNR in "bars" or in percentiles.

Re:The tools are called (0)

Anonymous Coward | more than 5 years ago | (#25663299)

The request asks no such thing, he simply wants to measure decay rate.

SMART over time (2, Interesting)

tepples (727027) | more than 5 years ago | (#25663573)

The request asks no such thing, he simply wants to measure decay rate.

The method of dd+diff can tell only whether the disc has decayed or has not decayed: 1 bit of information. Something that can read C1/C2 error rates, like the program Wanker mentioned [slashdot.org] , gives much more information that can be used to give a better idea of how much decay has happened before it becomes unreadable. Plotting this over time gives (ta-da) the rate of decay.

dvdisaster (5, Informative)

Anonymous Coward | more than 5 years ago | (#25662633)

You should probably try dvdisaster [dvdisaster.net] . it can test media, and can create (on disk or external) redundancy data, which can be used to recover later.
It's also open source, so you could probably coerce it to export some more information

Nero (1)

asc99c (938635) | more than 5 years ago | (#25662641)

Nero has a test utility, but I've not really found the results to be all that useful.

I get similar results from both unreadable discs that are 8 years old and stuff that I think is high quality Verbatim discs burned this year.

Re:Nero (1)

billcopc (196330) | more than 5 years ago | (#25663685)

Nero's test accuracy is highly dependent on the DVD drive you use. A number of drives on the market give unreliable PI/PO data, some of them deliberately to make the drive seem better than it really is.

Whadya expect, this junk's all made in Taiwan...

I highly recommend using Archival Grade Media (5, Insightful)

Phizzle (1109923) | more than 5 years ago | (#25662655)

Archival Grade Media makes a HUGE difference for backing up important data. It is not very expensive and widely available.

Re:I highly recommend using Archival Grade Media (4, Interesting)

Kamokazi (1080091) | more than 5 years ago | (#25663575)

Also looking for Taiyo Yuden brand helps (or anything made in Japan...that should be TY just rebranded). Every knowledgable board I've looked over on the subject has recommended them, and I have never had a single one of their disks out of probably 200 now be bad from the start. Unfortunately I don't have any 'old' disks to test. I keep most of my data backed up on hard drives.

Re:I highly recommend using Archival Grade Media (2, Interesting)

n1ckml007 (683046) | more than 5 years ago | (#25664005)

Does TY make DL discs?

CDCheck (2, Interesting)

Anonymous Coward | more than 5 years ago | (#25662661)

http://www.kvipu.com/CDCheck/

Create a CRC file for the CD. Saved me more than once.

It's ok... (1, Insightful)

Anonymous Coward | more than 5 years ago | (#25662679)

just hash the cd and you are golden. Like my apples during the fall.

Re:It's ok... (4, Interesting)

0100010001010011 (652467) | more than 5 years ago | (#25662895)

RAID5 for CDs? Is there anything where I can burn 3 CDs with a 'set' of data. When I want to restore my data I just put in each disk sequentially and then it does some RAID5 magic and spits out my data?

Be a cool project, IMHO.

Re:It's ok... (1)

RobertM1968 (951074) | more than 5 years ago | (#25662967)

I suspect it would be even simpler to make one or two backups instead.

Re:It's ok... (1)

Amouth (879122) | more than 5 years ago | (#25663317)

so your suggesting raid1 instead of raid5? that would increase the number of CD/DVD's needing to be stored consideribly.

this really isn't that bad of an idea for burning a backup file that spans multible CD/DVD's

i can see several diffrent ways it could be done.. question is who has the time and will to make it - if someone did come up with it i think i might use it

Re:It's ok... (4, Informative)

hjf (703092) | more than 5 years ago | (#25663023)

http://dar.linux.free.fr/ [linux.free.fr] try dar. It's like tar but for disks. it also generates PAR files (FEC data) which can help rebuild damaged media.

Re:It's ok... (0)

Anonymous Coward | more than 5 years ago | (#25663537)

RAID5 for CDs? Is there anything where I can burn 3 CDs with a 'set' of data. ...

was working on something like that. had trouble getting my drive to *even* mount the experimental damaged disk. if you here something about this .. submit a story!

not possible (0)

Anonymous Coward | more than 5 years ago | (#25662683)

Oh, please we all know cdr is for volatile data. Only the fabric-made discs long enough. Use HDD or SSD.

Re:not possible (3, Insightful)

Kagura (843695) | more than 5 years ago | (#25662743)

HDD are not infallible or "long lasting", but they are certainly far more convenient to deal with than CD-R and DVD-Rs.

dvdisaster (1, Redundant)

cpghost (719344) | more than 5 years ago | (#25662685)

dvdiaster [dvdisaster.net] has a utility to check for back sectors.

Re:dvdisaster (1, Funny)

Anonymous Coward | more than 5 years ago | (#25662835)

Your grammar and/or spelling is very back...

Re:dvdisaster (2, Funny)

cpghost (719344) | more than 5 years ago | (#25662947)

I'm missing a tool to scan for brain/attention decay...

Re:dvdisaster (1)

Darth_brooks (180756) | more than 5 years ago | (#25663639)

You could just remove it and scan for changes that way. I removed mine. The easy part was getting the brain out. The hard part was getting the brain out.....ahahahahahaha.

par2 (4, Informative)

Drinking Bleach (975757) | more than 5 years ago | (#25662691)

Whenever I back up important data, I use par2. If the disc has I/O errors, I just make a full image with dd_rescue (skips past bad blocks, whereas dd will just halt operation) and run "par2 verify" on it. If it's really important, I always verify the integrity no matter what (I've even done it on discs 2 days old, and sometimes, due to the reliability of CD/DVD-R media, it even has errors to repair).

Re:par2 (4, Interesting)

Waffle Iron (339739) | more than 5 years ago | (#25662991)

If it's really important, I always verify the integrity no matter what

I do that even if it's not important. I have a script which creates an md5 checksum file for a directory tree and adds it to the directory, and I always run it before burning a CD or DVD. Once burned, I verify the checksum on two different computers.

There have been a few times that the computer that burned the disc successfully verified a new disc, but a different one didn't. When that has happened, I trashed that disc and made a new one.

Sometimes I wonder if a lot of the reports of "deteriorating discs" are actually cases where someone burned a coaster in the first place, and just never happened to try to read or verify the data until years later.

Re:par2 (1)

xaxa (988988) | more than 5 years ago | (#25663337)

I do the same, except I don't have a script to make checksums for a directory tree, as it's a one-liner with Zsh:

md5sum **/*(.) > Checksums.md5

The (.) restricts the match to only normal files, the ** specifies a recursive match.

Re:par2 (4, Insightful)

Drinking Bleach (975757) | more than 5 years ago | (#25663529)

The problem with md5, is that it does nothing to repair broken data. It's great when you download something and find out it's bad so you try again, but for long-term data storage, knowing that your data is corrupt doesn't do you a whole lot of good. Which is why I recommended par2, it can both verify and (more importantly) repair data.

Re:par2 (3, Insightful)

Fast Thick Pants (1081517) | more than 5 years ago | (#25663937)

I've used par2 for this purpose, and it's not bad. It doesn't support multiple directories -- you have to create separate parity data for each directory on the CD. It also has no support for restoring any filesystem metadata, only the file names and contents.

I've also used dvdisaster, and I think it has some advantages. It creates a single block of error correction from the entire disc image, so it includes any filesystem information on the disc. It can use existing media in the drive, or an .iso file. The error correction data can then be appended to the .iso file before burning (assuming you've calculated the size correctly.)

I'd really like to see dvdistater's method become a standard feature of CD burning software, with the presumption that most people would want to add error correction to their discs if there's free space. Operating systems could check for this data when reading a CD and automatically use it to detect and correct read errors.

I'd really love to see this system adopted by software companies, music labels and movie studios -- but of course they'd much rather have a shot at selling you another copy of the disc you scratched.

Error-Proofing Data With Reed-Solomon Codes (5, Informative)

MarkoNo5 (139955) | more than 5 years ago | (#25662695)

The following tool allows you to track the failure rate of your media, and allows you to recover the files and replace the cd/dvd when it starts failing. http://hardware.slashdot.org/article.pl?sid=08/08/03/197254 [slashdot.org]

CDCheck (0)

Anonymous Coward | more than 5 years ago | (#25662747)

I use CDCheck. http://www.kvipu.com/CDCheck/ [kvipu.com] It may be enough for the task.

I'm going to ignore your question entirely (1, Offtopic)

einer (459199) | more than 5 years ago | (#25662757)

And suggest that instead of using CD-R's anymore, you buy some 1TB portable drives and keep them backed up. I don't know your application and you don't explain it, so this is more of a statement about how crap CD-R's are for archiving anything at all, ever. If you have important data on a CD-R, back it up asap.

Mod parent up! (5, Insightful)

GroundBounce (20126) | more than 5 years ago | (#25663285)

I have many gigs of digital photos and I have also more-or-less moved away from optical media for backup and switched to HDD. As the original poster mentioned, most of the "information" you find on the net about archival longevity of optical media is personal anecdotes or pet theories, and good hard data on archival longevity of CD-R or DVD+-R is hard to find. My own personal experience is that name brand discs do have fewer problems than cheap "house brands", but it's hard to quantify or say much beyond that.

Backing up to hard drives has a number of advantages:

1. It's a heck of a lot easier - in most cases of personal data backup, a few 1TB HDDs will hold all the data you need to back up, so there's no need to manage boxes of 100's of discs. I usually back up the same data onto two HDDs, and store one of them in a firesafe. If you're really worried, you can store one of them offsite.

2. Since no media will last forever, you will *always* need to roll your data over to new media every so many years. With HDDs, its *much* easier to roll your data over to new media every 5 or 6 years. Think of transferring two or three HDD's to a new HDD (by the time you roll over the data, the new HDD will probably hold all the data from those two or three older HDDs), compared to re-organizing and re-burning hundreds (or more) of CDs or DVDs.

The bottom line is that if a few HDDs don't hold enough data for your needs, then backing up to optical media will be totally out of the question anyway, and you will probably need to use tape.

Re:I'm going to ignore your question entirely (1)

g253 (855070) | more than 5 years ago | (#25663385)

Oh gosh, not again. This is the same as suggesting to install Ubuntu when someone has a windows-related issue.

Once and for all : the answer to "how to make FOO work better for me" is not "you should use BAR instead"!

Re:I'm going to ignore your question entirely (1)

Paralizer (792155) | more than 5 years ago | (#25663569)

Use tapes, hard drives fail all the time. Or you could get a nice NAS with a bunch of hdd's in some ultra redundant RAID configuration. Personally I would go with the NAS, but now you're getting into the couple hundred dollars range and it's not as portable as CD-R's or tapes.

Backing up from one hdd to another is a silly idea. If that's the most viable solution for you you might as well go RAID-1 so at least you always have a mirrored copy (I do this on my home machine and it works fine for me).

Save them again with long lasting solutions (4, Informative)

Maxwell42 (594898) | more than 5 years ago | (#25662765)

If you consider your data worth it, have enough time and enough money, you should probably re-burn/re-save them to long lasting media.

There was a previous post on askslashdot about this subject.
http://ask.slashdot.org/article.pl?sid=08/08/27/2119252 [slashdot.org]

My suggestion was to use Plasmon "Century-Disc" :
http://slashdot.org/comments.pl?sid=914095&cid=24784787 [slashdot.org]
(even though I have never tried it myself)

Suggestions (1)

Zontar_Thing_From_Ve (949321) | more than 5 years ago | (#25662769)

Nero has various tools that might be useful. I'm not really into this sort of thing as the people who are into it are generally off the deep end and take it way too seriously. The CD-R Freaks website might have some people who have helpful suggestions.

I have CD-Rs that are 7 years old that still work. In fact, I've never found a failure. You might consider using PAR to make PAR2 files for your CD-Rs so you can recover the data if it's important to you. You'll need to make those PAR2 files at the time of burn. And I would very strongly suggest that you ONLY use Verbatim or Taiyo Yuden media and consider every other brand to be suspect.

Ask people in the music industry... (0)

Anonymous Coward | more than 5 years ago | (#25662773)

A bunch of my old CD's are still playing with no problems (albeit ones I treated well and are virtually scratchless.) Perhaps someone in the know of how CD's are burned in a commercial fashion can give some pointers for higher quality methods at home.

Re:Ask people in the music industry... (4, Informative)

Drinking Bleach (975757) | more than 5 years ago | (#25663013)

CDs aren't burned for commercial distribution, they're pressed.

Re:Ask people in the music industry... (1, Funny)

Anonymous Coward | more than 5 years ago | (#25663993)

CDs aren't burned for commercial distribution, they're pressed.

So you're suggesting that I send my CD's to the dry-cleaners with my pants and get them pressed and that would make them last? Just how dumb do you think I am - the crease would ruin them!

Re:Ask people in the music industry... (3, Informative)

Rob Riggs (6418) | more than 5 years ago | (#25663179)

Commercial CDs are not burned. They are stamped. [wikipedia.org]

Try asking the media companies (1)

sunking2 (521698) | more than 5 years ago | (#25662775)

If you have a high failure rate then its because you are using crappy media. Just like buying heaper casette tapes strethed faster than the more expensive, the cheaper the media, the less reliable its going to be. Unless you plan on continually verify disks randomly I don't really understand the point of testing the media other than to generate some useless numbers. Call a company, find the one with the best actual rating for your price and refresh every 75% of that. I guess its conceivable that certain burners are more brutal on media than others, but I think in the end it comes down to quality media you are buying.

Re:Try asking the media companies (1)

waveformwafflehouse (1221950) | more than 5 years ago | (#25663917)

A climate chamber test [cdmediaworld.com] of most major cd media brands was done around 1999. An interesting read at the very least.

Handle with care (3, Funny)

kcdoodle (754976) | more than 5 years ago | (#25662777)

Never, ever had a CD die on me due to old age. I have burnt CDs that are probably older than you.

The only 2 reasons I have ever had a CD die.
1. Bad burn.
2. Dropped it/scratched it.

Okay, I really have only had one reason CDs die:
1. I can be somewhat of a dumb-ass.

Re:Handle with care (1)

xaxa (988988) | more than 5 years ago | (#25663397)

Never, ever had a CD die on me due to old age. I have burnt CDs that are probably older than you.

Wow, I feel old -- is the average age that low round here?

Add PAR2 files (2, Informative)

Still an AC (1390693) | more than 5 years ago | (#25662779)

When archiving data to CD or DVD I use a program call Quick Par [quickpar.org.uk] to generate recovery files that I can use to repair the data on the disc if it becomes damaged.
It is based on the same recovery tech that RAID systems w/ parity drives use, and is mostly used to repair Usenet downloads. I usually put 4GB of data and 400MB of PAR2 recovery files on the disc. This will allow ~10% data loss before recovery is not possible. Also I dont have to worry about the TrueCrypt vol becoming damaged and unusable as well.

Re:Add PAR2 files (0)

Anonymous Coward | more than 5 years ago | (#25663127)

Uh no. It is a much slower tech than RAID systems, but it is much better.

Papyrus / OCR solution (1, Funny)

Anonymous Coward | more than 5 years ago | (#25662859)

Print it all out on Papyrus burry in an Egyptian tomb then use an OCR solution.

I use gold disks and burn at slow speed still no guarantee.

Clay tablets work well.

How about bringing back punch cards?

Laser inscribe data on Copper plates or better yet modern stainless steel would last.

Re:Papyrus / OCR solution (1)

WinPimp2K (301497) | more than 5 years ago | (#25664001)

"How about bringing back punch cards?"

I was with you up till there, but punch cards bring back painful memories for me - causing an emergency shutdown of my humor processor.

Some interesting statistics(which I shamelessly stole from a quick search)

based on a weight per card of 2.42 grams per card. (cards are punched so the blank weight would "be slightly higher)

cards/Gb = 1024^3 / 80 = 13,421,772
tons/Gb = ( 13,421,772 * 2.42 ) / 453.59(grams/lbs) = 35.8 tons

volume - the cards are close to the wieght of water - they float, but not by much so assume a specific gravity of 1.0 1 GB would require 35.8 cubic meteres of space allowing no easy access.

Of course, if you are using it for archiving say DVD quality videos, you will want quite a few gigabytes of storage. Did you budget for a climate controlled room (fricken huge warehouse really) with airlocks and positive overpressure to keep paper eating insects out? The stuff I worked with was about 500 megabytes, stored in a non climate-controlled warehouse - this means the cards would expand with moisture and heat and then jam in the reader - destroying the card. And yes, there were also problems with insects eating the damn cards too. Google bookworm - or failing that just go talk to a person who buys books at a regular (not college)used bookstore.

So, a BLU-Ray quality movie (lets say 10 GB) would take 134 million cards, and would weigh about 360 tons (and require 360+ cubic meteres of storage space). Let's not even talk about read/write speed for the card reader/punch, nor the possibility of dropping the cards. There is also the matter of regular wear and tear on the hardware.

One other consideration might be the cost. IBM punch cards used to sell for 30-40 dollars per box. So that BLU-Ray backup would require about 70K boxes of punch cards and cost somewhere north of 2 million dollars.

I do not think that punch cards are looking like a viable backup medium. And the last time I checked, Egyptian tombs were in rather short supply.

Now metal punch cards made of a relatively non-reactive metal and stored in a vacuum might work a little better - especially if one posits that the use of vacuum storage would require a very heavy degree of automation. It might even be possible to automate the production of the blank cards - actually, I believe that a teletype ribbon might work, plus the "confetti" could be easily recycled.
Hmm.. lots of aluminum, enormous amounts of vacuum, heavy automation - I think this is beginning to sound a lot like the Google Moonbase.

Try the CDFreaks Forums (4, Informative)

Wanker (17907) | more than 5 years ago | (#25662865)

The obsessed people at CDFreaks can help. Here's a link to their FAQ on CD-R media:

http://club.cdfreaks.com/f33/media-faq-61943/ [cdfreaks.com]

In other places in the cdfreaks forums, you'll find links to tools that can read the C1/C2 error rates. One of the simplest is "readcd", part of the "cdrecord" programs on Linux.

In the DVD world, Lite-On and Plextor both make proprietary programs to read the media-level error rates which only work with their own drives. Lite-On has a Linux version of theirs.

Re:Try the CDFreaks Forums (2, Informative)

Opyros (1153335) | more than 5 years ago | (#25663629)

Note that on Debian-derived distros, the equivalent of "readcd" is called "readom".

Re:Try the CDFreaks Forums (1)

peterd11 (800684) | more than 5 years ago | (#25663701)

I have Plextor drives and software, and check errors rates on burns from time to time. I've found that with a good quality drive, like Pioneer or Plextor, and good media, like Taiyo-Yuden, the error rate is consistently low. As with most things, you get what you pay for, and using good drives and media is cheap insurance.

Tape (2, Interesting)

sexconker (1179573) | more than 5 years ago | (#25662899)

Backups? Use tape.

Optical media is inherently shitty.

If you want to get the best out of it:
Buy good media.
Burn at a slower speed.
Verify the data after burning it.
Store it well. A hard case, and a cool, dry location away from the sun are all you really need.

If you want to test the quality of a disc, go ahead and use any of the tools recommended here.

If you want to harden your discs, go ahead and use any of the CRC tools recommended here.

But really, you shouldn't be using optical media as anything other than a cheap delivery medium. If you need to send stuff to people and you need them to have a copy of it indefinitely, tell them to make a damned copy of it, or give them 2 copies, or keep an ISO and send them a copy when theirs fails.

Re:Tape (1)

jaguth (1067484) | more than 5 years ago | (#25663661)

Magnetic Tape media doesn't last very long; 10 years maximum for a corporation. Its good for disaster recover solutions for 5-10 years, but anything longer, than hard disc is the best solution.

Re:Tape (2, Insightful)

rho (6063) | more than 5 years ago | (#25663821)

Tape isn't better than optical, necessarily. All backup mediums require testing to ensure reliability, which generally means restoring from backup.

If your data is critical, keep it in several places at the same time, and as closely synced as you can manage. Hard drive, mirrored to another hard drive, backed up to an external hard drive, swap out external drive for another every week (stored off-site), run incremental backups to tape nightly, use an online backup service like rsync.net or Carbonite. Even then you're not assured of complete data integrity, but it's not too shabby and not horrifically expensive.

If your jobs can be archived onto CD/DVDs, then doing that is one more safety net. If you don't want to go through a long, drawn-out process of running CRC checks or whatever on the optical media, simply burning it twice on two different computers is an option. If that's not possible, burning it twice on two different known-good brands is better than nothing.

Professional Advice (5, Informative)

polyomninym (648843) | more than 5 years ago | (#25662937)

I work with CD/DVD and related technology as a profession. I analyze, QC, and mass duplicate media by the thousands for extreme and critical field use, every day. My best advice to you is to use Taiyo-Yuden (TY) media, always. I've seen mixed results and bad burns from Mitsui and MAM-A gold, Kodak, and the like. The TY dye type has a proven longer longevity than any other so far. I also suggest burning all of your audio CD's at 16X, this affect what's called single-beam readers. Also, it insures higher integrity of the burn. Burn 16X DVD's at 8X to increase the write integrity.

What others say about is CDCheck is true, use it along with this advice. Use Plextools Pro on a PX-716 drive if you can find one. It seems to be more accurate than Nero tools. Use Plextools to check the C1, C2, and CU rates. If the graph is half-way to the top of the reading, back that disc up. As cheap as media is, I suggest burning more than one copy, storing the image on an external archive hardrive. When burning, don't use overburning. You lose some integrity for error correction.

Store your media in a cool dry place, on it's side. Avoid humidity, light, and heat when you can. Remember, the best analysis tools in the industry are very expensive for individuals. Take a look at CATs if you are interested in learning more about optical media testing. Best wishes!

Re:Professional Advice (1)

ihatethetv (935399) | more than 5 years ago | (#25663129)

do you work for TY?

Ok ok...im just giving you a hard time...I can vouch for TY media quality in my personal experience.

Re:Professional Advice (2, Interesting)

polyomninym (648843) | more than 5 years ago | (#25663349)

Interestingly enough, I work for the first company to ever produce and sell pre-formatted floppy discs. We're right down the street from M$ in Redmond, WA. I use many different brands for different uses and client needs. HA, I don't work for TY, and that's why I shamelessly promote them ;) I also suggest using Verbatim, the dye and quality are very similar. In all of my experience, TY is the best. BTW, optical media manufacturers come see us as the perfect testing ground for end use because we do everything you can to optical media, down to print and packaging. (dsgi.com) Cheers!

Re:Professional Advice (1)

Mprx (82435) | more than 5 years ago | (#25663733)

I've once scanned a YUDEN000T02 DVD+R with *zero* parity inner failures, so the outer layer of error correction isn't used at all. Best media I've ever seen.

But where to buy TY? (1)

kalpol (714519) | more than 5 years ago | (#25663283)

Taiyo-yuden media is not labeled as such. What brands are consistently made by TY?

Re:But where to buy TY? (1)

polyomninym (648843) | more than 5 years ago | (#25663393)

Many companies buy mass qty's of TY and re-brand them. You can get great deals with (dsgi.com) we ship globally as well. If you are interested, make sure you pick the surface that your printer can handle. We have all of the edge to edge Everest print surfaced TY's and Inkjet printable surfaces. Happy burning :)

Re:But where to buy TY? (3, Informative)

AxemRed (755470) | more than 5 years ago | (#25663681)

You can buy Taiyo-Yuden media at...

http://www.supermediastore.com/ [supermediastore.com]

That's where I got mine. I haven't had a bad burn yet.

Re:But where to buy TY? (1)

mobby_6kl (668092) | more than 5 years ago | (#25663861)

Some of Verbatim DVD+Rs (and probably CD-Rs too, but I haven't used those in a few years) are actually made by TY, some of their other ones are Mitsubishi Chemical (Verbatim's parent company), which in my experience are also very good. Some types were also made by other OEMs which are supposedly not as good, but I haven't had any problems with any of the Verbatim branded media. Of course, if you look around you can find TY branded media as well, like at the places mentioned in the other two posts.

Re:Professional Advice (0)

Anonymous Coward | more than 5 years ago | (#25663621)

Does anyone have any experience with the Kodak Ultima media? (Is it still being sold?) It's supposed to last for 100 years:

http://www.kodak.com/global/en/service/faqs/faq1632.shtml

Single-beam and three-beam pickups (1)

tepples (727027) | more than 5 years ago | (#25663781)

I also suggest burning all of your audio CD's at 16X

Did you mean 16X, or "16X or slower"? So-called 52X recorders start at about 20X and reach 52X when they reach the outside of the disc with a greater linear velocity. Forcing 16X makes the recorder use a constant linear velocity over the whole disc to minimize the effects of vibration. But is there anything special about 16X that makes it better than 12X?

this affect what's called single-beam readers.

I just wanted to add something to help people understand what your post means. In cheap mechanisms, used in cheap CDDA players, the pickup moves the laser beam back and forth across the data track, centering the head wherever it finds the strongest signal. This is a "single-beam pickup". Because it uses one beam for signal and tracking, the signal level in the parts where less of the beam is over the data is lower, making the data noisier. This strains the error-correcting code more, and uncorrectable errors show up sooner. More expensive mechanisms, used in high-quality CDDA players and computer optical drives, split the beam into three parts: inside, middle, and outside. In such a "three-beam pickup" or "split-beam pickup", the data comes from the middle beam, and the inside and outside beams are used only for tracking, moving the head toward the stronger signal.

Learn more about pickup strategies [mscience.com]

Re:Single-beam and three-beam pickups (1)

Scaba (183684) | more than 5 years ago | (#25663921)

Learn more about pickup strategies

Finally, the secret of how to meet girls! Oh, wait...

Re:Single-beam and three-beam pickups (1)

polyomninym (648843) | more than 5 years ago | (#25663967)

Thank you for sharing this info with everyone. Nice clarification. I've heard the term "wobble" used to describe what those single-beam readers are referencing. I see that you are keen to mscience.com as well. Jerome Hartke was trying to sell his business to us and some of our associates a while back. Heh, I just don't have time to maintain something like that. It may still be up for grabs. Cheers.

Re:Professional Advice (1)

the eric conspiracy (20178) | more than 5 years ago | (#25663809)

I have seen bad CD burns from Mitsui Gold, usually on a burner that is not working particularly well or on blank media that is a bit old. However I have never (7 years now) had a Mitsui Gold CD go bad on me in storage.

use CD/DVD speed (4, Informative)

YesIAmAScript (886271) | more than 5 years ago | (#25662939)

http://www.cdspeed2000.com/ [cdspeed2000.com]

You need certain brands of optical drives, but with them and this program (and others), you can see the PI/PO or C1/C2 correction (I can't remember which is for CD and which is for DVD) rates on a per-sector basis on your disc. As the rates rise, the disc is going bad, becoming marginally readable and you can copy the disc before it becomes unreadable.

You can find out which drives to buy at http://cdfreaks.com/ [cdfreaks.com] . The terminology on there for a drive that can do this is a "scanning drive".

I have no idea if you will find that your correction rates are rising over time.

Re:use CD/DVD speed (2, Informative)

sricetx (806767) | more than 5 years ago | (#25663959)

FYI - Nero CD Speed version 4.7.7.16 runs fine in Linux under recent versions of Wine. The newer version (callled Disc Speed, not CD Speed) does not work under Wine.

I've used it with two different Liteon SATA drives: a Liteon 20A3S and a Liteon 20A1L. Both of these drives (and I believe, Plextors) support scanning for jitter. When you run CDSpeed, the test you want is the Disc Quality tab. Click Advanced and then check the DVD Jitter checkbox. This test will give a good an indication of the quality of the disc.

In my experience, Verbatim Datalife Plus (media code: MCC) are really good discs. CMC Magnetics media vary widely, some are okay, others are garbage.

It's amazing and simple (1)

Anonymous Coward | more than 5 years ago | (#25662971)

NAME
              cdck - simple CD/DVD check program

SYNOPSIS
              cdck [-d /dev/devname] [-i] [-v] [-p] [-o plot-file.dat]

DESCRIPTION
              -d CD/DVD device name, default is /dev/cdrom

              -i Print CD/DVD information and quit, perform no timings

              -p Save data for gnuplot(1) program

              -o specify plot file, ./cdck-plot.dat is default

              -V Print version

              -v Verbose operations

Verify after burning (1)

jd142 (129673) | more than 5 years ago | (#25663009)

Are you sure that the discs really did burn correctly 3 years ago? Some burning software, Windows I'm looking at you, doesn't report errors correctly.

For stuff I care about, I always have Nero verify the data when done burning.

Backup your CDs to floppy disks (0)

Anonymous Coward | more than 5 years ago | (#25663035)

If it's something really important, you should back up your critical CD data onto realiable floppy disks and store them in the back seat of your car.

Make Two? (1)

RayMarron (657336) | more than 5 years ago | (#25663055)

I imagine if it's important, and you don't mind doubling the cost of your media, you could just burn two. Then, you have something to compare against, and if parts of it go bad, hopefully the same parts won't go bad on the other one. CD-RAID? :) You could even go so far as to make sure the two disks are from two different manufacturers.

Betcha didn't think the AC would know! (1)

Anonymous Coward | more than 5 years ago | (#25663135)

readcd [die.net] -c2scan

You'll need a drive that supports such a scan, although that's true for any such utility.

The best part is you don't even need an md5sum, par, or anything like that. The verification is built right into the disc.

Might be helpful (1)

Toll_Free (1295136) | more than 5 years ago | (#25663229)

.sfv verification might be helpful.

I'm not sure what utilities are available on *nix, but winsfv has always worked for me.

Generates a checksum file by file, and then dumps the checksums into a file. Simple, fast, and works great.

I know there are .sfv shell scripts all over the web, as I used to use them on my ftp sites, to verify the integrity of files transferred against the list of checksums. Files didn't match checksum, files automagically deleted.

When making up your disk images, you could .sfv checksum the entire dir structure, and have a file in the root of the cd with the sfv checksums. Then when you want to verify, just run the sfv check against the file in question and compare it to the original.

Works great to ensure nobody's changed anything, too. One bit screws up the checksum.

--Toll_Free

Re:Might be helpful (1)

JustNiz (692889) | more than 5 years ago | (#25663353)

Thats too high-level. The utility you mention only scans files, meaning degradation in unused or 'system' areas of the CD wouldn't get reported. Also, it only reports errors after any lower-level error-recovery strategy has failed. Consequently it does a good job of hiding actual disk degradation.

The type of utility that is needed to give an accurate, unaffected report of degradation is a whole-disk scan that reports errors even before any error-recovery strategy is attempted.

mass produced CDs last far longer (1)

Eravnrekaree (467752) | more than 5 years ago | (#25663281)

CD-Rs have a shorter lifespan from mass produced CDs due to different manufacturing techniques. Mass produced CDs last much, much longer. I have CDs that are 15-20 years old and still are perfectly fine. Regular CDs are mass produced by stamping a pattern into a layer in the CD, this yields something much more reliable than the burn in used in CD-Rs. the average age of CD-R is 3-5 years it seems. CDs can last for decades, maybe even centuries.

Re:mass produced CDs last far longer (1)

TeknoHog (164938) | more than 5 years ago | (#25663515)

So, when making backups of my data, I should have them mass produced instead?

Not looking at the true problem?? (1)

geekmux (1040042) | more than 5 years ago | (#25663289)

Yes, there are endless discussions regarding type of media, burners, software, rates, dyes, etc. but due to various levels of inconsistency in manufacturing (how dyes are applied, quality control, RoHS, etc.), why bother trying to gather this type of data?

My recommendation? Look towards either Cloud solutions or other technologies (RAID arrays) or PROVEN backup media (LTO) for VERY long-term storage. Unless you plan on keeping your backup hardware, software, and media static over the lifetime of your analysis and storage, tying up tons of man-hours proving that one or two types of media/burners work perfectly, and then find in two years the software/hardware vendors make changes invalidating all of your testing seems rather pointless.

That being said, I do agree with the others. TY media pretty much performs flawless for me, and I try and store a backup copy in the back of my safe inside my Data Center at work to maximize long-term storage conditions. For me long term is less than 2 years on CDs and DVDs due to paranoia. Media is cheap. Data loss is not.

qpxtool (1)

mmontour (2208) | more than 5 years ago | (#25663335)

http://qpxtool.sourceforge.net [sourceforge.net] - Linux program for performing low-level quality measurements on CDs and DVDs. It only works with some drive models, so check the supported hardware list.

Titanium Plates © if your data matters (5, Funny)

Phizzle (1109923) | more than 5 years ago | (#25663343)

Take a page from the book of Church© of© Scientology©®(TM) and engrave your data on Titanium© Plates© and store it in Gold© Vault©. I apologize in advance to the Church© of© Scientology©®(TM) if I didnt use enough Copyright©®(TM) symbols while referring to Them (©?). Please do not sue me. © (TM) ®

Re:Titanium Plates © if your data matters (0)

Anonymous Coward | more than 5 years ago | (#25663563)

Please provide your physical address to facilitate serving you...

The Church of Scientology©®(TM) Legal Department

burn twice, rar with parity (1)

ClintJCL (264898) | more than 5 years ago | (#25663439)

I burn 2 copies of everything, an archive, and a "for use". If I start to have trouble with a "for use" disc, then I have two options:

1) Get my archive disc out, and re-burn a new copy.

2) Copy whatever files I still care about (some old stuff can die, some can't) to my harddrive, treat as new data, and re-burn on ANOTHER two discs.

Also, when I RAR anything (backups of dvds or large file repositories, for example), I use the option adds 8 percent parity to the file.

This is similar to your fancy-schmancy "par" tools except it is proprietary to WinRAR. But I figure: If 8% of my disc is unreadable, getting 100% of my data back would be pretty damn cool.

What helps the most, however, is having 5TB of LAN space.

A hard-drive remains the most reliable (2, Insightful)

Anonymous Coward | more than 5 years ago | (#25663469)

I think that the most reliable way to backup your data is to use a USB hard drive changed every 1/2 years.

Actually I use two : one at my parents in Europe, one at my place in Canada.

A hard drive is much more reliable than any CDR/DVDR, and if your data is important it's worth it.

Just my two cents.

David

Slightly OT, but... (1)

maugle (1369813) | more than 5 years ago | (#25663479)

How well is, say, a USB flash drive suited to archival purposes? They're pretty hardy little things, so I'd expect them to last longer than your average burned CD.

Re:Slightly OT, but... (0)

Anonymous Coward | more than 5 years ago | (#25663597)

Probably fine. Until you sit on it and break it.

Thus the lesson: If something is important, you'll back it up:

- On multiple devices

- In multiple locations

suggest you include a checksum file (0)

Anonymous Coward | more than 5 years ago | (#25663513)

I suggest that you include a plain text file in the root directory with checksums for all the other files on the CD. Any of the MD5/SHA1 utilities would be fine, such as "md5summer":

http://www.md5summer.org/

Despite other comments in this forum, I would suggest that the CD be recorded in a standard ISO/Joliet file format and not using backup/compression programs. For my own use, I wrote a fancier checksum utility that produces XML format with multiple checksums:

http://www.download.com/Compare-Folders-Java-/3000-2248_4-10895789.html

(That's an obvious self-serving promotion.) The advantage to a plain-text checksum file is that years later you can use another utility to verify the checksums.

Here's an idea... (1)

Mysticalfruit (533341) | more than 5 years ago | (#25663577)

What you could do is setup a system that would do the following...

1. Create a CD and then using your favorite hashing algorithm generate either a whole disk hash or a per sector hash and store this information in a database.

2. Take a disk out of storage, analyze the disk and if all the hashes match up, use this disk to make a copy. Then rerun step 1 on the second disk to verify that all it's hashes match up and if they do, store both.

3. Setup up a routine where once a month you pull a volume out of your archive and verify it's hashes. If that volume fails, go to the second disk, hope like hell it's hashes are good and if they are, duplicate off the second disk.

Backup (1)

Godji (957148) | more than 5 years ago | (#25663627)

Several hard disk drives and ZFS (which has automatic error detection and correction). Backup problem solved.

Re:Backup (1)

f16c (13581) | more than 5 years ago | (#25663803)

This does no good if the drive dies or the file system is stomped on by the OS. As said above: Multiple copies in multiple locations. Either do this or kiss your data goodby right now...

Long term storage (1)

magamiako1 (1026318) | more than 5 years ago | (#25663857)

When you need storage and reliability for the long term, there's no substitute.

http://www.historyforkids.org/learn/westasia/literature/cuneiform.jpg

WTF?! Why are you using CD's? (1)

mrgodzilla (730416) | more than 5 years ago | (#25663923)

You can buy a hard drive that will store 1000 CD's for about $100. Buy a 2 or 3 and use some form of raid and you should never lose any data for as long as you tend to the rare disk failure now and then. This thread should be about making a cheap home raid array for backup and the best methods for doing so.. how often to scrub the array, etc.. Reminds me of a colleague that wanted to buy this expensive tape backup system, robot type that auto-mounted tapes.. when we had this awesome, unused netapp sitting in the data center.. wtf?!

Old Technology is sometimes best (1)

UnknowingFool (672806) | more than 5 years ago | (#25663973)

I feel that making backup copies using punchcards will ensure that they last a long time. Especially if you can get them associated with an election controversy like the 2000 Florida Election Results. Just make sure that they have hanging chads. :P

Backup all your discs to Hard Drive (0)

Anonymous Coward | more than 5 years ago | (#25664011)

Hard drive space is so cheap that there is no reason not to.

Get a mirrored set of hard drives, and back it all up. CDs are almost as bad as floppies in terms of retention length.

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