EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: edy on November 17, 2015, 05:29:53 pm
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I have a problem with many of my older CD-R's and I'm wondering if anyone has noticed the same issue.
Most of them are getting CRC errors (cyclic redundancy check) *only* on the files that are near the outer-most edge of the disc (the last files written to the disc). The files were burned in alphabetical order, as a single session and then disc closed.... Now, almost 5 years later, when I try to copy them back to the hard-drive, it can handle almost everything but the last 40-50 MB.
I wrote the CD-R's as a single session and closed the discs. Most are about 3-5 years old. Many are supposedly 700 MB, so I filled them. I don't remember what I used to burn them, it may have either been Nero or Power2Go which came with my ASUS laptop. And I am pretty sure that I had them verify the disc after burn.
So a few things may be happening here (from my limited knowledge of optical drives):
1) The drive I am reading them with is somehow "running out of calibration" sync as it nears the outer-most tracks on the burned CD-R. I've tried other drives as well but not had any better luck. The drive I'm using is oriented vertically, the one I burned in was horizontally-mounted.
2) The media I used is crap. However, I used Staples brand, Mitsumi, Maxell, TDK and Philips. Both rated at many times burn speed and 700 MB. And if it was crap, why did it verify properly? I haven't noticed any trends yet, but I'll keep looking.
3) The burner software I used was crap and lied about verification or was only able to verify on the drive on which it was burned (see #4).
4) The drive I originally wrote the CD-R on had some quirk which allowed it to read/write out near the edge of the disk but every other drive doesn't follow the same quirk so it has problems.
5) The media is degrading from the edge of the disc towards the inside, or the centrifugal force or simply the increased radius is causing the most "wobble" out near the edge of the disc leading to problems reading the outer-most 50 MB or so.
So in summary, I have about 100+ CD-R's all burned around the same time, various brands, all on the same computer and as a single session closed CD-R in alphabetical order file listings. I am able to copy about 50% of the CD-R's no problem.
The other 50% always seem to copy almost to the end of the CD-R.... but the last 50 MB or so (it varies) on different brand CD-R's give me CRC errors on the files. So I have to use IsoBuster to try to copy the files... There are always errors, which I need to IGNORE to continue copying.
One other thing that might be important. The files are typically 8-10 large MP3 mix files... each is about 60-100 MB in size, usually 1-2 hours worth of music. So when there is an issue with the CD-R, it can copy usually the first bunch of files, and then the last MP3 file (usually 60-80 MB in size) has the error about half way through it.
I choose to IGNORE the error in IsoBuster and it copies the file, but when I listen to it there are glitches throughout most of the MP3 beyond that point. I can still listen to it, but there are obviously problems.
I am not too troubled by this because it is just MP3 music, so if I lose some I don't really care. But I just want to know for my own sake and the future of my more important files what is happening here. Any thoughts?
EDIT:
One other thing... Old fingerprint smudges near the edge of the CD, maybe the oil had deteriorated or hardened on the surface or something.
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CDs are 650 megabytes. Many disks and burner software allowed you to exceed this. Have you tried different drives.
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Try a new drive, preferably a DVD one, and use horizontally. If you only have USB use a cheap USB drive adaptor, which will interface the drive, and which has it's own ( nasty but good enough) power supply. Clean the disks with a lint free cloth, and try again.
I did try out some backups done the same way, but these were onto Verbatim archive grade disks, and all that i tried would read the whole 700M no problem, though it was drive dependant, a brand new drive di best, an older one was very iffy. then data erasure was performed on the disk pack, using the microwave to make some magic sparks and 30 second data erasure, followed by a trip through the shredder.
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CD-R's age fast, they only last up to 10 years. Not even that long when written in full speed. And only a weeks or months days if left in the sun.
They are ideal to quickly hand off some file to someone. They are horrible for archiving, due to the need for duplicity, and that you'd need a lot to store some serious data.
I have disc's about 5 years old here, they are all starting to lose their metallic coating and crinkle, there are also cracks in the inner layer. Obviously, this starts on the outside.
You can try to read them at the slowest speed you can.
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That's very disappointing. I think many of us were led to believe they lasted longer. Even tape lasts longer. It's back to hard drives now for me.... Several for duplication just in case. They are cheap enough, 2 TB drive will easily hold about 3000+ CD's.... and take up a fraction of the space, and costs <$100.
I think I will need to do the same with my DVD collection. Assuming 4.3 GB per DVD, then 2 TB should hold about 465+ DVD's. They are probably going to have the same issues, if not already... Time to move everything back over to Hard Drives.
(3000 x 700 MB = 2100000 MB ~ 2000 GB ~ 2 TB)
(465 x 4.3 GB ~ 2000 GB ~ 2 TB)
PS - I know there are differences with 1024 MB = 1 GB or 1000 MB = 1 GB definition, and same for GB to TB conversion.
My point is valid nonetheless... I can't seem to see the point of optical media anymore, unless we are hit by some electromagnetic disturbance which wipes out all our hard-drives.
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Non writable optical media lasts much longer because it is not written by a laser but made by injection molding. Though I'm not sure about blu-rays.
Cheap method of distributing one to many when not all your customers have fiber.
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Air starts leaking in from the outer edge and oxidises the information-carrying dye layer.
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i have not burned CD/DVDs in a while but for some reason i never filled them up... always left about 500mb free on DVDs and about 50mb free on CDs, i also never burned at the maximum speed and never had an issue
it could be the drive you used to burn them was slightly out of spec somehow and made problem disks for the next drive or combined with possible cheap media. I have used CDRs where the top aluminium (reflective) layer is so thin and poorly protected it was very easy to scratch and flake off so the quality of the media and the dye they used is very important.
try different drives and turning down the read speed to 1X
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Are you sure the device you read them with is not faulty? Such a thing happens when the shaft in the bearing of the motor becomes loose. This affects reading of the outer tracks much more than inner ones because the small angle of the vibration is amplified by the long distance from it's source, thus resulting in significant absolute movement on the outer side. But yes, CD/DVD media is not reliable, especially re-writable types.
Worth to mention that the disc which cannot be read in one reader, very often can be read in another.
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If it was media deterioration I would expect to see errors distributed across the surface. I suggest trying some different drives. Fingerprints or other damage was my first thought. Edges are more prone to damage.
I have 20+ year old disks that can still be read. (Kodak-Gold) so they can last pretty well.
+1 to everything above. I have a few 10 year old CD/DVD drives that are working just fine (and some are not) and I also have 1993~1994 CD media recorded in 1x, 2x and 4x that is still alive and kicking today.
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I had some CD-Rs that had become unreadable in everything I tried... CD-ROM, DVD-ROM, DVD-RW drives. Some would just refuse to mount the discs. Mostly they would read part of the disc then slow to a crawl, then stop altogether. Then I tried an old CD-R/DVD-ROM combo drive from an old Mac. This thing could read all those old rotten CD-Rs without issue, at full speed. I was amazed. I have held on to that drive "just in case". So definitely try multiple drives, you just might find one that works.
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Non writable optical media lasts much longer because it is not written by a laser but made by injection molding.
Not always. In the 1980s there were millions of replicated (stamped) laserdiscs that suffered "laser rot" caused by a chemical reaction. Indeed, the symptoms of deterioration in 12cm discs like delamination and wrinkling have nothing to do with laser exposure, they are caused by defective manufacturing. Replicated discs are not protected from that.
If the discs are physically fine but lose data, then the stability of the dyes is to blame. Since 2000, most CDRs are made with azo dyes instead of the original types developed in the 1980s. Their lifetime is simply not as good, but they were required to hit higher writing speeds like 24x. ReWritable media shouldn't have those problems because they are not dye based, but use perovskite crystals with different physical states.
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I have a problem with many of my older CD-R's and I'm wondering if anyone has noticed the same issue.
2) The media I used is crap. However, I used Staples brand, Mitsumi, Maxell, TDK and Philips. Both rated at many times burn speed and 700 MB. And if it was crap, why did it verify properly? I haven't noticed any trends yet, but I'll keep looking.
You nailed it right on the head as far as I am concerned. A lot of the media is CRAP! It doesn't make any difference whose "brand" you are using! From what I have determined there are only a few manufacturers of CDR Media in the world. A couple that come to mind are CMC Magnetics Corporation, Ritek, Moser Baer India, Ltd, and a few others I can't recall right now. From what I can see your brand names go to these guys who make the CDRs and brand them with their name, i.e. Maxell, Staples, Verbatium, Hewlett Packard and so on. There is NO WAY to know if they are going to be readable in a few years or not! I have some Memorex that I got originally when I started using CDRs in 1996 that are still working just fine. There are other CDRs that have failed with in a year. Staples comes to mind, made by CMC, as foremost. My experience is that CMC Magnetics manufactures CRAP. I have some from CMC that are still working 15 years later and I have some that failed in a year. It is a hit and miss proposition with CMC. I don't know if it is poor quality control with the dies, bad application die to the media, bad reflective layer or what. I have seen recorded media that I can see the logo from the bottom of the CD, i.e. "Staples". When this happens the CDR cannot be read anymore. This condition does NOT exist when I recorded them, but happens over time. CMC is "Lot" dependent, by that I mean that if you look at the manufacturers "Lot codes" that are in the plastic around the inside guide hole you can pretty much tell that if one CDR has failed, the rest from that same "Lot" number will be unreadable also. The problem is that you cannot tell who manufactured the CDR media until you read that information from the CDR with a diagnostic program which will give you that information. I use "DVDINFOPRO". By then of course you have opened the package and it becomes non-returnable, just because you don't like the manufacturer.
I have verified each CDR with DVDINFOPRO after I burn it, but then a year later it is unreadable. You are correct in that sometimes this seems to affect the data at the outside edge of the disk and then works it's way in over time.
Bottom line here is.... Don't use CDR for permanent backup or any purpose in which you want the information to be available ever again. Hard Disks are the answer. I have backed up all of my CDRs to my USB 4 TB hard drives, as well as I could as I discovered during the backup that many had failed.
IMHO
Bill
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IMHO, field-writable optical media were never the "archival quality" they were advertised to be. 5 years is really pushing it for any expectation of 100% recovery. People with good disks older than that were just plain lucky. Hard drives are OK for "near-line" backup, but they are not "archival", either. Many drives simply fail sitting on the shelf. I have a growing pile of hard drives that simply won't even spin up.
Since field-writable (and re-writable) optical discs have the "groove" molded-in, it seems unlikely that the problem at the outer periphery could be caused by mechanical "runout" error in tracking the groove. The read/write laser/head is dynamically positioned by reference to the edges of the "groove".
So it makes me think the problem is more likely with the reflectivity. Presumably the surface of the disc is not dirty, scratched, etc? As others have already mentioned there have been problems with the dye, AND with the reflective surface (typically sputtered aluminum). And remember that CDs have the reflective surface immediately under the "label" with no mechanical protection. DVDs have the reflective surface actually sandwiched in the middle of two discs bonded together, so they are much less susceptible to mechanical damage to the "data layer".
And certainly, the faster the discs were written, the lower the likely contrast ratio between one and zero. And back when I used to write many discs, I used Taiyo-Yuden brand exclusively as they had demonstrably better quality.
I would certainly try to read the discs on as many different drives as I could access. Some drives are better at reading marginal data than others.
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Long-term backup is a problem. It wasn't so bad >=10 years ago when most people could easily back up their stuff to a single drive or DVD's. Now that people have multiple terabytes of stuff, it's harder to keep more than one or two copies as volumes of media quickly build up.
I have just over 10TB of data. My first line of defence is the RAID itself (which isn't designed to protect against corrupted files). My only other backup at the moment is LTO2 tape (1 copy of my file server is across 43 tapes or something like that).
My next server upgrade will at least double that capacity. I don't just have spare hard disks laying around but I need to get onto it and do something. I'll probably stick with LTO but a newer generation once the price of second hand units come down a bit.
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I just noticed something very interesting.
I had a bunch of CD-R's and about 50% copied ok... another 50% were always getting CRC errors often near the end of the disk. No correlation to brand at all.
So I had this one CD-R that was getting CRC's in the middle of the disk, so I decided to wipe it really hard with a micro-fibre cloth and it read perfectly afterwards. And the only thing I could see on the surface was a tiny mark or fingerprint or something that I wouldn't even notice otherwise.
So either these disks or the drive are extremely sensitive to the marks, or they have "baked on" for several years and hard to remove or read through. Either way, I may try to wash my CD-R's and see if I can get any better results from the ones that had problems the first pass around.
EDIT: I also wonder if using Isopropanol will work (or dish soap?) or will it be too harsh on the disc surface. Also, will using a clear-coat spray/nail polish type material to fill in any micro-scratches help?
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I remember the game shop in town has a disc polish machine for scratched xbox and playstation games. Maybe that will work?
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It has to be the surface... not the drive or brand. I read about 3-4 CD-R's ok, then 1 or 2 crap out near the final outer tracks.... Then again I read about 2-3 CD-R's ok, and 1 has some issues on the outer files. So it is less than 50% affected.... probably close to 30% of my CD-R's have an issue reading the last 5% of the disc content on the disc. So overall I haven't lost much data.
It also doesn't matter what brand of disc. Mitsumi, Philips, Staples or TDK. None of them are those very "dark blue" surface ones... they are the lighter silvery green color. Maybe the dye is the problem. They are all from about the same age and burned on the same drive. The only explanation must be something on the discs affecting them randomly on the edge (old scum or prints that have degraded or pitted the surface). I can't see what else it could be, unless there was a problem originally writing the discs that was not detected or verified).
EDIT: Murphy strikes again. Between the time of the last post and now, I read 4 discs in a row without any problems. Different discs... and didn't clean any of them. And I could see they weren't perfectly clean either. Watch now that I say that, I'll get a bunch of bad discs again.
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I'm not a CD ROM expert, but it seems to me your problems with the outer edges could depend on whether the disk is rotating at a constant speed. The transfer rate section of the wiki page for CD ROM says that slower drives adjust the angular velocity to maintain the same linear speed of the media at the head as the head is repositioned. Above 12x, a constant angular velocity (CAV) is used, causing the outer edges of the media to have the highest linear speed with respect to the head. A higher linear speed would likely be more error prone.
https://en.wikipedia.org/wiki/CD-ROM (https://en.wikipedia.org/wiki/CD-ROM)
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I remember the game shop in town has a disc polish machine for scratched xbox and playstation games. Maybe that will work?
Yep, you would usually apply a slightly abrasive cream to the disk to polish out fine scratches. Toothpaste works well if you're desperate to get data off a disc (I've done it a few times).
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Explanation 6) The dyes in CD-R (and DVD-R) media is sensitive to light. If discs are stored in spindles, light leaks in the edged of the discs and degrades the dyes from the edge in (doesn't matter whether this is before or after burning).
Unwritten edge-damaged discs might burn fine and verify fine at the time, but were compromised already, and just normal aging pushed them beyond readability over time.
I do wholeheartedly agree with the recommendation to try more drives, including a true CD-RW (no DVD capability) drive if you can find one. (I've found that many models of DVD drives, but especially laptop drives, are really bad at reading marginal CD-Rs.) If you can find a Yamaha or Plextor CD-RW drive, those will have the highest chances of all. (I cried when Yamaha left the optical drive business...)