CD degradation.....

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scotty
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Re: CD degradation.....

Post by scotty »

Interesting,Also ive heard if you slap a dead fish and squirt tom sauce over a CD whist chanting Abbas The winner takes it all backwards absolutely nothing happens to the CD sound quality but if you indeed load it into your disk drive in your computer magical elves will sing Somewhere over the rainbow in Spanish.
buy a new CD Rob.Numpty.
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cjj
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Re: CD degradation.....

Post by cjj »

gibsonlp wrote:
cjj wrote:You can, of course, transfer your CDs to a hard disk in a non-compressed format such as WAV so you won't lose anything. This does take more disk space however. But, with terabyte (1000 Gigabyte) drives available these days for around $100, you can easily put more than 1200 CDs on a drive.

Of course, hard drives are also prone to failure, so you might want to buy a couple of them for backups. I'm not sure that the lifespan of the magnetic data on a hard drive is these days. Back when the density was much lower, it was pretty much infinite barring physical damage or high magnetic fields. But with the ultra high density of current disks, I'm not so sure...
If you leave a hard drive offlilne for a few years (about 8 years or so) you'll start it up to see it has been completely wiped off.
The magnetically stored data is simply being slowly wiped off by earth's magnetic core, when the drive is operating this is not a problem as it automatically fixes and re-writes "weak" magnetic parts of the data, but when the drive is offline - it will be gone eventually.
As I mentioned, back in the old days (when drives were sub gigabyte and I was designing disk drive electronics and high reliability disk storage arrays), this was not so much of a problem. As the magnetic "bits" get smaller, their overall magnetic field gets weaker and is more prone to the effects of other magnetic fields, etc. It wouldn't surprise me at all if 8 years or less was the limit these days...
I have NO idea what to do with those skinny stringed things... I'm just a bass player...
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Tarrbot
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Re: CD degradation.....

Post by Tarrbot »

cjj wrote:
gibsonlp wrote:
cjj wrote:You can, of course, transfer your CDs to a hard disk in a non-compressed format such as WAV so you won't lose anything. This does take more disk space however. But, with terabyte (1000 Gigabyte) drives available these days for around $100, you can easily put more than 1200 CDs on a drive.

Of course, hard drives are also prone to failure, so you might want to buy a couple of them for backups. I'm not sure that the lifespan of the magnetic data on a hard drive is these days. Back when the density was much lower, it was pretty much infinite barring physical damage or high magnetic fields. But with the ultra high density of current disks, I'm not so sure...
If you leave a hard drive offlilne for a few years (about 8 years or so) you'll start it up to see it has been completely wiped off.
The magnetically stored data is simply being slowly wiped off by earth's magnetic core, when the drive is operating this is not a problem as it automatically fixes and re-writes "weak" magnetic parts of the data, but when the drive is offline - it will be gone eventually.
As I mentioned, back in the old days (when drives were sub gigabyte and I was designing disk drive electronics and high reliability disk storage arrays), this was not so much of a problem. As the magnetic "bits" get smaller, their overall magnetic field gets weaker and is more prone to the effects of other magnetic fields, etc. It wouldn't surprise me at all if 8 years or less was the limit these days...
Areal density has increased quite a bit in the last decade but I can recall in 2000 and before where we were told that this "pixie dust" would increase the density even more.

It's great what we have now but I require not only areal density but speed--whether that is in spindle speed or low latency or even just overall IOPS. But until SSD arrays become 1) faster 2) less expensive and 3) more reliable, I will still use magnetic disks with mechanical parts in them. :(
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gibsonlp
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Re: CD degradation.....

Post by gibsonlp »

CJ: So you mean that the old 300MB drive I have in my closet for the past 12 years still has information on it??? I'll check it and tell you if it's true, I actually never bother checking it after discovering that they lose data with time...
So long and thanks for all the fish!
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cjj
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Re: CD degradation.....

Post by cjj »

It's possible, but there's a lot more to it than just time. Temperature, whatever magnetic fields might be drifting through the environment where they have been stored, and probably the biggest factor, the quality and whatnot of the disk itself. I know that for the storage arrays we were much more selective as to what drives we used (and we made all of them ourselves). I seem to recall that there were different types of magnetic materials, or maybe it was the case material, but I wasn't really in that end of the business. I remember the cheaper ones had the main cover made of a plastic material, kind of like a big sticker covering the platters, but the good ones had metal covers that were screwed down. But that was 20 some years ago.

Anyway, it's worth a try if you have them, you certainly won't hurt anything...
I have NO idea what to do with those skinny stringed things... I'm just a bass player...
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cjj
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Re: CD degradation.....

Post by cjj »

I should probably add that a lot of the stuff I'm remembering about longevity of the magnetics on disks was from from 5.25 inch drives. When we started going to the 3.5 inch drives, the costs were changing rapidly and drives started to be thought of as "throw away". The emphasis changed from having ultra high reliability drives to having easily changed, "hot swappable" drives so that failed drives could be replaced while everything was running.

The density, and hence the size of the magnetic areas on the platters has a lot to do with it. The raw storage volume is something else. We made lots of small drives (such as 300MB) that were exactly the same as larger drives, but with fewer platters in the stack. So, just because a drive has less storage capacity doesn't necessarily mean it has less density on the magnetic surface...
I have NO idea what to do with those skinny stringed things... I'm just a bass player...
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johnallg
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Re: CD degradation.....

Post by johnallg »

I have an old 286-based pc with two Seagate 48mb SCSI hard drives in it and it will still boot up to DOS, what I had on it when we used it. I haven't used that PC since my son was about 5 or 6 - he turned 23 a month ago.
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jingle_jangle
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Re: CD degradation.....

Post by jingle_jangle »

...back to CDs and DVDs...

This seems to be the definitive text on the topic:

http://www.itl.nist.gov/iad/894.05/docs ... gGuide.pdf

Based upon what this guide says, it would seem that DVDs are more stable for storage.
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Tarrbot
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Re: CD degradation.....

Post by Tarrbot »

jingle_jangle wrote:...back to CDs and DVDs...

This seems to be the definitive text on the topic:

http://www.itl.nist.gov/iad/894.05/docs ... gGuide.pdf

Based upon what this guide says, it would seem that DVDs are more stable for storage.
I think there are huge differences in what NIST and the general public define as "storage".

What I mean is that while NIST means cataloging and storing in an ideal environment, most of the general public means storage and potentially reusing the data in the near future. Those two definitions are normally completely different from each other in terms of media lifespan.

What matters to most people is retrieval of the data on the medium. Properly cared for media is the issue. Most people do not properly care for optical media and definitely would have issues caring for analog tape. I make assumptions here with these statements but these assumptions are based on my experience.

To go a step further, I've only ever seen 1 or 2 CDs fail due to damage. I've seen multiple DVDs (20-30) fail due to just slight blemishes. If you do Netflix at all for any length of time, you've had to send a disc back. I can guarantee it. Under normal use, DVDs are not a good storage medium. The areal density on the platter is too fine for small blemishes to take whereas the area density of a CD is much more "coarse/less fine" and can take a bit more abuse.

Regardless, if I were storing data long term, it would either be DVD or most likely analog tape backup. Each has its positives and negatives. I keep our entire companies data storage on tape backup and while a project manager at a Fortune 100 company, all of our data was kept on tape backups. There are many reasons for it but capacity was a huge one. I can store 1.6TB of data on one LTO-4 tape whereas even on a DL DVD, I'm only getting at best 9GB. That's 177 DVDs worth on one LTO-4 tape with proper compression. Even uncompressed on the LTO-4 tape, I get 800GB or 89 DVDs worth of data.

And that brings up data retrieval options. To properly get 89 DVDs worth of data back into service, I would have to stand there for days inserting discs... even in a DVD library array.

So, here's ultimately the question with NIST vs the general populace: How quickly do you want to retrieve your data and do you want to bet that within the "expected lifespan" of 50+ years of DVD vs analog tape that you will be able to find a better solution, even if it is another optical or analog format?

The general populace will more than likely take the analog tape option as it's more convenient and compact and quicker to access than DVD ever will be. Even with Blu-Ray become more widespread, it won't dent the analog tape market since analog tape and the devices that run them march forward in capacity as well.
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