CD-Recordable discs unreadable in less than two years

CDFreaks.com (by way of SlashDot) ^ | 19 August 2003 | Dennis

[RadioAstronomer]

What would it take to solve the problem so that future generations could read our stuff. The historians trying to study us 1000 years from now will no doubt be clueless as to what to do with material stored on our computers (if our computers are working then, which is not likely). And of course, our CD's will be long dead.

I have no idea. Scientific American did a huge write up on this problem.

[stands2reason]

Cool! I just read it a couple of weeks ago. Great book! I realized reading this thread that the last technology those monks would have been able to "save" couldn't have been much newer than mid-20th century anyway considering the type of data storage used. So in that way, the book is still quite relevant...

You never know, there might be a King of Denver someday....

[reagan_fanatic]

"Fan should be blowing on and cooling the underside of the HD. The electronics. This is the point of failure, not the spinning disks inside.."

Absolutely correct. I keep a fan on mine at all times.
Heat kills electronics.

[FReepaholic]

>>...You might be interested in the Internet WayBack Machine...<<

Hey, thanks! That's a great site!

Fun to see what Amazon.com looked like back in '96. Also the White House site on an all gray page. Ahhh..the good 'ol days!

[marlin]

the process for making cd roms and cd-r's is similar but different

but first a small primer - cd's are digital - meaning they are reading the functional equivalent of 1's and 0's - which in the case of cd's are called pits and lands

in a mass produced pressed cd a glass master is made of the original material to be produced - this is then made into a reverse negative stamp - which is put into the replication machine

in the replication machine the stamping process is done to a plastic disc - which is then coated with the relective layer - then coated with a lacquer - then silk screened with the label - then uv cured - the entire cycle takes about 4 seconds

for a cd-r the blank disc has 1 long spiral groove in it - it is then covered with an organic dye - typical cyanine, phtalocyanine or metalized azo - then with a lacquer coat - finally a printable cating may or may not be added

what happens over time with cd roms is that the normal atmospheric conditions allow water vapor to seap between the plastic layer and the lacqer layer and cause oxidation to occur - so dependent on your environment the process can take varying lengths of time

how the disc is read by the laser is that the cd reader is looking for the relflection delta - >70% - which changes the 1 to 0 or 0 to 1

the laser is reading straight up and down - so the angle is all important

when the cd rom starts oxidization the reflective surface no longer felects straight back - it aberates - which causes read errors

cd-rs use what is referred to as ablative technology - which is simply that the writing process fores a laser pulse which burns a whole in the dye layer - which is why it is called burning a cd - so that when the cd-r is then read by a reader the laser beam eith hits the organic layer and is absorbed - or goes through the burnt whole and reflects back - thus mimicing the pits and lands of the pressed cd

with a cd-r as the dye layer deteriorates the reflective delta changes and cases read error

also scratchs on the plastic side are not as catastrophic as cratches on the label side - as the lable side scratches can easily lead to either a scratch or a wrinkle in the reflective layer - which will cause read errors

of course gouges are a bad thing on either side

[FReepaholic]

>>...I am for micro-etching print (data) using lasers on metal or a hard plastic that will last for a million years...<<

How 'bout holographic storage inside a crystal??

[fqued]

You have over 6000 books? D---! I only have 3000.
But I also buy and sell antiquarian books. I like reading books that are a few hundred years old.

My 5 1/4 floppies are stored in the closet, unreadable; but my hand-written notes and manually typed papers are still easy to access.

[RadioAstronomer]

You have over 6000 books? D---! I only have 3000.

That is a bunch also! :-)

My 5 1/4 floppies are stored in the closet, unreadable; but my hand-written notes and manually typed papers are still easy to access.

Easy enough to get a 5 1/4 drive and dump em to a hard drive. What I did. :-)

My papers also are quite readable. Print is still a great way of archiving. :-)

[Prince Charles]

Tip: If you're using a Sharpie marker (or similar) to write on the label side of the disc you're playing with fire. The dyes from the permanent marker can seep through to the dye layer of the disc and corrupt it. Buy markers that use water-based pigment and are specifically made for use with disc media.

[aruanan]

To be honest this is quite stunning. The amount of valuable information lost is staggering, this will compound the problem. People assumed (as did I) that CD-ROMs were a viable backup alternative to tape.

I've had some sound CDs I've made develop weird characteristics. I've wondered what would happen to the unprotected surface due to oxidation. I've been able to read some Imation CDs I made of my electron microscope inages and thesis stuff about 2 years ago. But these CDs have been in a fairly stable, low humidity environment since they were created. At least my plastic coated audio CDs from the late 80's are still playing fine. I think to be safe(r), I'm going to buy a couple of big hard drives and copy everything back to them.

[anymouse]

ping.

[Physicist]

I was just about ready to do my first "burn" today or tomorrow of music to clear my hard drive. But my goodness, if this is true, that isn't good.

I wouldn't worry about it for that purpose. If some of the bits become unreadable on an audio CD--hell, if many of the bits become unreadable--you probably won't be able to hear the difference, and if you're burning from MP3 files, there probably won't even be a difference, unless you are using a wastefully high bitrate (or VBR).

Contrast this with a data CD: flip one bit in an executable program, and it very likely becomes unusable. Flip one bit in a bank of data, and right answers become wrong. (Ask RadioAstronomer how important that can be.)

I've just started burning audio CDs myself. I'm a longtime subscriber to Emusic.com (which I recommend to every true music lover), and have assembled a (figuratively) massive library of MP3 albums. Now I can tote my treasures with me anywhere; that's the real value of it. If storage space is your main issue, you might want to reconsider: 32 MP3 (VBR) albums take up about 2 gigabytes of space on my system. Disk storage costs about a dollar per gigabyte these days. The cheapest storage case I've found for 32 CDs costs about $10, not counting the media.

[RadioAstronomer]

CD players use an error corretion scheme/code (ECC) called the Cross-Interleave Reed Solomon Code. This allows the player to recover lost bits in the playback of data. Just as a side note, the Voyager II Spacecraft Used a Reed Solomon code for its ECC.

Here is a nice site to explore these codes a bit further:

http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Writing+Quality&index=5

[rwfromkansas]

I like the portability aspect. I still have 50 gig on my HD even with tons of mp3's, so space is not really the issue, though part of it is a desire to clean house a little.

[null and void]

Absolutely top notch short story. The best last line of any short story I've ever read. Actually, sort of chilling.

Yes quite good. But I find the following last line my personal favorite, and chilling...

"And strangest of all is it to hold my wife's hand again, and to think that I have counted her, and that she has counted me, among the dead."

[null and void]

Not as chilling as the short story; "A Walk in the Dark" though! WOW that was some story too!

YIKES! I forgot that one!

[rogue yam]

Ummm... 9 track tape too! LOLOLOL!

That's what you get when you take an 8-track tape and then turn it up to eleven!

[RadioAstronomer]

That's what you get when you take an 8-track tape and then turn it up to eleven!

LOL! I picked up a 9 track player with a PC interface a number of years ago. I am not even sure it works anymore. The coolest thing was that it came with a 9 track calculator (slide rule) for computing bits/inch depending on tape speed and bit density.

[yhwhsman]

Did you get that drive recently? I wouldn't mind having a drive like that, actually still have 5-1/4" discs lyiny around from when I was in college in the early 80's.

Yhwhsman

[yhwhsman]

One of my favorite's of all time, as well as the sequel. I'll puke if you tell me there's more volumes to the story.

Yhwhsman