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Reliability of CD-RW Discs 41

Posted by Cliff from the the-psersistence-of-data dept.
Fruck asks: "I've been using CD-RW discs to store my important data for the last year, with no problems. However, I fear that one day, somehow the data could be gone because of general wear and tear on the disk. I'm wondering if anyone else who uses CD-RW heavily has experienced any problems with data loss... " Interesting question. Wonder which one fares better: CD-Rs or CD-RWs?
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Reliability of CD-RW Discs More

Reliability of CD-RW Discs

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  • On CD-R reliability. (Score:1)

    by Anonymous Coward
    I can speak on that issue. Don't rely on them. They can fade badly, even in darkness at a constant 65 degrees. They are not appropriate archival media. The reason that I know this is that the company that I work for acquired a major compeditor in an oddly friendly merger last year. Their IT operations are a nightmare -- decentralized, uncontrolled, unaccountable, fragmented, and so on. And they are running SAP. Yes, this has been interesting. One of the things that the decentralized divisions did was plan their own backup policies. Some were using Zip disks, so help me God. Some were using CD-Rs, and that is how I came to be familiar with how quickly they will fade. Kept at 40 degrees in darkness, they may last 15 years. Otherwise, count on 5 years. The military won't use them, the major oil companies won't use them, many state governments are issuing the same warnings that they issued a few years ago about Zips disks (i.e., we don't know their lifespan or reliability, please use tape), and people are discovering the hard way that their data ain't readable any more. The issue is that CD-Rs haven't been cheap enough for broad use. Zips were cheaper and out all over, and so people could discover their shortcoming en masse pretty fast. CD-Rs are only now getting that widespread. They are cool -- I have one and love it -- but they are no substitute for tape (QIC or DLT or the IBM tapes, NOT 4mm and 8mm) or MO (of any sort, really) for permanence. If you need to keep data a long time, like 50+ years, you need MO. Anyway, YMMV, but I can tell you that we are, right now, transferring huge amounts of data over from Zip disks, Jazz disks, and CD-Rs, and all are having dead media rates of 20%. Not fun. None of that stuff is going to the salt mine!

  • CD-R Reliability (Score:1)

    by Anonymous Coward
    I work for THE major oilwell data archiver in Canada and we did extensive testing of media when we first started FIVE years ago. We have thousands of CD-Rs of raw and compressed data that are handled on an infrequent basis. All data problems to date have been the result of the user (dropped, scratched, oily finger prints, etc.), 70% are TDK, 5% Maxell, and 25% are Kodak. I should also mention that we make two copies of every disc and second is stored off-site in a vault, these have never failed.
  • I got a 10 pack of Mr. Data CD-RWs. They were the cheapest available at the time. One was defective out of the box. Your best defense is to diff -r your CDs.
  • Careful -- most CD-RW discs have a very finite (and frequently lower than you'd expect) number of writes that can be performed in a given area. If you're constantly re-arranging and saving data to your CD-RW's in this manner, it will wear it out rather quickly.

    I'm afraid I don't have a number, but I remember something in the neighborhood of 1000 writes? Maybe somebody else can comment.
  • Just out of curiosity, since the bulk of the disc itself just seems to be transparent plastic, is there a common method for re-surfacing the bottom of the disc? If a bunch of surface scratches don't actually damage the media, one should be able to "sand" and buff the bottom side of the disc and be able to read their data again, yes? Is there a published method or product for doing this?
  • If you want to see what your data is really on, put a cd-r into to the microwave for about 3 to 5 seconds. When it comes out, you will discover that the label peels off in pieces, and that your precious data is being written onto the backside of the labels. That's right, the data layer is not in the disk at all. All it would take is damage to the label and your data is nuked!

    Acutally, I thought that CD-R changed the opacity of the plastic rather than the reflective label, which was why they were light sensitive in the first place.

    Real CDs have an aluminum layer which is pitted at the 1/4 wavelength "depth" IIRC.
  • My experience has been that CD-RW is rather particular about the drives used not just to write to them, but also about the drives used to read them (as in one CD-RW drive may not read disks created in a different one).

    CD-R is much less particular. Most DVD-ROM drives won't read them (although that is improving with newer drives). I have CD-R media three years old (both data and audio), many of which have sat on the dashboard of my van for weeks or even months (not direct sunlight, but wildly varying temperatures, -10 up to 130F. I have yet to encounter any reported errors.

    I am pretty dang careful in creation though... disks remain sealed until ready to be written to and are blown with canned air to remove any dust prior to being recorded.
  • Since everybody and his brother are selling CD-RW drives now and CD-R drives seem to have disappeared practically overnight I'm assuming that CD-R's hold up much better than CD-RW's?

    If you don't have off-site backup, you don't have backup.

    "But hey, doesn't everyone have a Liebert?" I give up, what's a Liebert?

  • Luckily, most of us don't use our archival CD-R's inside a microwave ;-)
  • That is, 65 cents per disc, not 65 cents per 100 dicss.
  • Whoah. Really? I've got quite a few CD-Rs that are about 4 years old, and none have failed. I'd assume some sort of Gaussian distribution of failures. Are your temperatures given in Fahrenheit or Celcius?

    Don't know if anyone has any evidence to support this, but I've heard that the ones that appear gold on the bottom layer are supposed to last longer. The ones that are dark blue are supposed to be the next most durable, and the silver ones are supposed to be the least durable. Of course, this could easily be a marketing ploy.

    A friend that has a pretty extensive collection of Grateful Dead shows (400+ shows straight from the boards, most with 2 discs) swears by the Maxell ones with the gold bottoms. Since I buy by the 100, and the price difference per disk is about 65 cents, I follow his advice.

  • Re:Zip (Score:1)

    by cswan ( 6058 )
    Couldn't have ANYTHING to do with those good samaritans at Iomega, could it? :)

    I would place Zip discs at the bottom of my recommended media list. They're slightly more reliable than a floppy, but floppies have the added advantage of not being able to destroy your drive when they go bad (yes, I'm referring to the ClickO'Death.)

  • My experiance is that any zip drive older than 3 years of age is still working. Anything newer than that has a 50% fail rate and will always fail with one year of heavy use. I've dealt with about 20 of the things. My company originally got 5 epson drives 3 years ago (all still working) and then later had to get the Iomega drives. The Iomega drives are the ones failing (they are all two years old or newer) and they are the source of all media corruption as near as I can tell as well.

    YMMV. At least I hope it would since based on what I've seen I must be doing something wrong

  • Just don't use packet writing software with CD-RWs. I've had the experience of getting a blue screen (back in my Windows days) and trashing all the data on the disk. I wasn't impressed.
  • Liebert: n. A large commercial air conditioner used in a lot of server rooms / computer labs. My high school had one for the computer lab. We kinda made it our pet. Yes we were dorks. It was just fun to see the "high humidity" light go on and hear liebert kick into action.
  • If you want to see what your data is really on, put a cd-r into to the microwave for about 3 to 5 seconds. When it comes out, you will discover that the label peels off in pieces, and that your precious data is being written onto the backside of the labels. That's right, the data layer is not in the disk at all. All it would take is damage to the label and your data is nuked!
  • I know that the Adaptec software avoids writing in the same spot repeatively if possible; this is to conserve disc life.
  • okay.

    my cd-rs are all now in the fridge. the mp3s are safe.
  • Don't know if anyone has any evidence to support this, but I've heard that the ones that appear gold...

    This reminds me of claims I heard about 10 years ago that if you colored the edges of CDs with permanent markers, you'd get better sound quality. This claim might be similarly mythical, or there could be some long-term color drift that affects the accuracy of readings due to color bias of the lasers themselves.

    There were also rumors that the original CDs would decay and cease to work, but as far as I can see there's no failure rate of old CDs (15+ yrs) caused by aging. I don't doubt the author's claims, nor would I take them as gospel. It stands to reason that CD-R is more reliable than CD-RW in the long run, and that you shouldn't trust untested factors (lifespan of CD-Rs) in your long-range planning unless you have evidence to back it up.
  • My new computer came with a program that lets you convert a CD-RW into a disk, so you can just go file/save into that location *like a zip disk*, Anyway, I'm a little shacky on the matter and haven't actually used it. Any comments?

    Oh Yea, you can run ScanDisk and Defrag on them too.
  • Well, heres the problem with those.

    1. I've had mulitple zip disks lost to the "Click of Death"

    2. Super Disks are REALLLY slow.

    Whick makes the CD-RW's a good idea.
  • There is a utility program. Its on download.com but i'm not sure what it's called. It worked great for an RW that got corruppted on me once. Also i think(not sure at all) that you can mount an RW in linux in such a way that it ignores errors.
  • Better idea
    • put them in the freezer and remove the little light bulb.
    • Padlock the door.
    • Swallow the key.
    Your data wil be safe.

  • If you tape cardboard over your microwave's inside light and turn off the lights in your house, the 3 second CD-R lightning show is nice.

    I trust my DLT - only backup device I trust at all. It's so consistently reliable - media and drive mechanism.

    If I have any doubts or questions, then its not a good backup device. I through money into backups, in the hope I never really need them.
  • Well, have you heard about the click of death?

    Here's a link: Information on the click of death [grc.com]


    Iomega is digging it's own grave.


    "Now you can see that evil will triumph, because good is dumb!"
  • I have used RW sporadically for major backups, and I have no complaints, as the discs are always stored in a cool, dark place. However, I have noticed a high ( 10-15% ) failure rate on frequently used and abused media. (This is versus a 2-5% observed failure rate of R media) Of course, I am exceedingly paranoid during the creation/burn process; alcohol wipes, Air-in-a-can, and don't even think of breaking the seal until absolutly needed. Additionally, some brands or RW media (Ricoh) have a much, much shorter lifespan than others (Memorex), while others (TDK) never completly fail and only acquire more 'quirks' along their lifespan.
  • Written on the label!? Actually its an organic dye thats heat or light sensative (not sure which) when you pop them in the microwave the dye becomes transparent or burns away. (better explination at the Ricoh site)
  • ... which means for backups and essential archives these things are bad news. I've had several CD-RW disks get corrupted, and there seems to be no version of something like "Norton Utilities" for CD-RW media.

    If you've got a CD-RW drive, then you also have a CD-R burner. At well under a USA buck a blank these days, do yourself a favor and just blow out your backups and archival datasets out to a CD-R disk, which you'll be able to read later on just about any CDROM drive on the planet.
  • A friend of mine once bought a spray on solution for this purpose. It was a while ago, so I don't know the name or what the product was made of, but it did help on some audio CDs to eliminate skipping. I guess the stuff just kinda filled in the cracks.
  • DVD-rom, if its 2nd gen or later should be reading cd-r just fine. If someone sold you a first gen in the last year or so, they are scum :)



    Anonymous Coward, get it? :)
  • Yep, they haven't gone anywhere. And if you want serious 6X or 8X burn speeds, getting one without R/W can save $100 or more.

    Try somewhere like www.hypermicro.com for 6x24 teacs and 3 different 8x20 brands. There is a 8x2x20 plextor and a 6x4x24 yamaha but notice the price ;)

    R/W costs more, is read by less drives, and so far it seems the consensus is that it isn't as reliable as plain old R.

    Soooo, some of us don't need r/W, and would rather just get our R in half the time or less.



    Anonymous Coward, get it? :)
  • Packet writing is really lame, unless you don't understand how to use a disc-burning app like CDRWin or Easy CD Creator (this smells like a Windows app). Packet writers like DirectCD are handy but slow, and the UDF disc format it uses can't be read by many older drives.

    If you want to store files somewhere other than on the HDD or the network, use a high-volume, fully rewritable storage medium like SuperDisk.

    The Zip/SuperDisk issue is another thread altogether though...
  • I have CD-R's that dont have a lable on them so it must be stored on a layer just under the label. Also CD-R's from a company called Great Quality suck realy realy hard. so do their CD-RW's
  • The utility on download.com is CD-R Diagnostic available from CD-ROM Productions [cdrom-prod.com]. An excellent tool for analyzing, inspecting and recovering data from CD-R and CD-RW media. No, it doesn't analyze your drive, just the media.
  • the laser actually causes a chemical change in the reflective surface.

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