cd-rom lifespan?

Question

I'm looking to find out about the effective lifespan of a cd-rom with music wriiten on it. How long is this? .Is the quality of the disc an issue? . Or th filetype?. Why would a cd-rom have a shorter lifespan than a shopbought cd.

Answer 1

Commercial CDs have essentially an unlimited lifespan if they are manufactured and treated right, as they are produced in a similar manner to vinyl record "masters" - they are patterns pressed into a piece of metal, encased in a (relatively thick) chunk of transparent plastic.
if it's been produced properly - good quality materials and machinery, no splits or gaps in the plastic-metal-plastic "sandwich" that can cause the infamous "Laser Rot" that some laserdiscs had (incredibly, vanishingly rare with CDs) - and it's always handled with care (finger in the centre hole, thumb on the edge, going direct box - player - box), kept in it's box away from direct sunlight, not scratched etc.... then the claim printed in the sleevenotes of many 1980s audio CDs that it will "provide a lifetime of listening enjoyment" is correct. I have a few discs in my collection that have had treatment that way (e.g. things i got in my early teens when they seemed incredibly expensive, and i didn't even have my own player, just the parents') and they've lasted the best part of 15 years without significant degredation so far. Whereas some things that my aunt's kids have (younger, more spoilt, and less respectful of CDs having some value and awe attached) are scratchy, jumpy, and next to unusable after only about 18 months!
(not to mention the four discs i've destroyed myself through carelessness - but out of 200+ i still know exactly which ones they were and what i'll be more careful to avoid in future, e.g. putting them in your pocket at the beach, or letting the box fly around loose in the back of a car)

CDRs are a much more variable quantity. For starters the manufacturing process of the blanks can span the entire range of highly precision-controlled, best-materials, industrial grade output such as seen with expensive "audio mastering" discs from big name manufacturers, down to bulk trash ones dished out en masse by chinese knock-off shops using whatever materials they had to hand that week. Most likely you'll have the latter as their product gets bought, rebranded and sold even by some prestigious firms sometimes (which is why, following a certain backup incident, i won't be buying Memorex again). This makes their overall shelf life decidedly unknown unless you have the technical knowledge of identifying what batch is what, and the details attached. It can be drastically short even if kept in a cupboard, and i've had some (very cheap - though still £2/disc at the time!) CDRWs used for once-a-month backups develop HOLES in their media after only a year or so, of being kept in a "cool, dark, dry" place, and effectively sealed airtight in a storage box... seriously bad news! Whereas some of those topflight manufacturers make bold claims like their Double Gold Archive discs can withstand fifty years of continual out-of-box direct sunlight and still be perfectly readable (though you'll certainly pay steeply for it).

Another problem for CDRs, and particularly CDRWs, is the writing method. You DO quite literally "burn" the information into them... instead of a set of indentations that disrupts the laserbeam as in a regular CD, the CDR has a dye layer that the write laser burns through and alters the reflectiveness, simulating the same effect. However this isn't exactly the most reliable method always, the dye layer means total reflective power is lowered (making them hard to read in some players), and exposure to strong sunlight can decay the dye. CDRWs have it worse as they use a "phase change" media so you can re-write them - basically the laser causes a chemical change on one pass at a certain beam strength, writing the information (and changing the reflective properties), and a stronger beam reverts it to normal, erasing information (a standard strength beam merely "reads" the info)... their reflective power is even lower, and sunlight has a risk of disrupting or erasing the phase change pattern. So if you want to keep your CDRs a long time you really must keep them boxed - in jewel cases with the black plastic backing and a dark coloured inlay sheet, in a cupboard.

Of course most people won't treat their CDRs with that kind of respect, so their lives are quite limited and their long-term reliability can dip even below that previous champion of high-speed corruption, the HD floppy disc. I've even found recently some moderately cheap discs that I burned a load of MP3s on in 2001 are nearing the limits of usability (taking multiple passes to read some files, and in fact failing completely on one or two), even though they've been treated pretty well - of course, not perfectly though. They haven't been out in the sun long periods - they're mainly as an archive than a common use thing, only coming down rarely to copy tunes onto a new computer or to be played in a set-top DVD player - but they have been in semitransparent coloured cases on a CD shelf, which will still be letting some light in (evidenced by a slight sunbleaching pattern on the titling ink!). Only about a five year shelf life - not good for long term storage in the slightest. Good job i have them all on a hard drive too, from which i will have to re-burn the files onto new discs, probably DVDs this time (wonder what THEIR reliability is like?). Oddly it seems that hard discs are far more reliable long-term (got a 40mb one in a computer from 1987 that's still chugging along nicely!), with optical discs maybe more useful as short term backup to cover when the hard drive finally breaks down. That, or Magneto-optical... which is kind of the halfway point between the two technologies and traditionally has been the medium of choice for e.g. medical image archiving. Bloody expensive, however. You may be as well to turn your information into a benign, hard to detect virus that circles the internet servers of the world continually.

Incidentally you mention the "filetype"..... actually this CAN have an impact on the long term storage. There's two parts to it - 1/ the raw disc format, 2/ the file format itself.

1/ Audio CDs tend to use "all" of the disc capacity, with only the basic common error correction found in all CDs, as it matters far less if there's a small skip. CDROMs, however, take the 2352-byte sectors of audio (and video-CD*) discs and chop the capacity down quite a bit, only storing 2048 bytes there, with the remaining 304 used for copious amounts of error correction. "Packet writing" CDRWs lower this further, altering the basic structure of the disc itself to have 2048 byte sectors, error correction areas, and a small blank portion in between to aid accurate laser positioning when writing / erasing a chunk of data. Which is why you may buy a "74 minute" CDRW, and find you can get about 740mb of audio data on it, but only 650mb of computer files, or a paltry 540mb or so if used in Packet mode. Each type is a fair bit more error-tolerant than the one before it, but perversely, thanks to the even greater sensitivity of their contents (you can lose a significant amount of audio or video data and not notice - hence mpeg compression - but one bit of one byte wrong in a CDROM program can send the computer haywire; a similar error on a packet disc could misalign the laser and erase several files accidentally).
* actually VCD uses 2336 because it does have a teeny bit extra EC, and already uses MPEG anyway, but let's let that slide.

2/ File format. Now, there's usually only one for Audio, and as mentioned that's fault tolerant. Your favourite CD may have all kinds of unrecoverable errors on it causing many clicks, pops and scratches, but their typical effect is so small and so brief compared to that of a scratch on a vinyl record, and the CD player's circuitry programmed to "smooth over" the gap so cleverly, that you wouldn't notice until you ran it through an analyser. The exception to this is CD+G, the audio/kareoke format - but even then, as it doesn't use any compression or store any programs, the worst that can happen is some minor title image corruption or a few letters wrong in a word / timing going out of sync.
When it comes to CDROM, it depends on what you've saved, in what format, and how good your drive is. If it can recover a scratch gracefully, no files should be affected. If it flat refuses to transfer the information of a broken file, then you'll have trouble reading the data no matter the format. But if it passes it in "broken" form (quite common), that's where the fun starts. A few wrong characters in a program or a compressed file can cause all kinds of wierdness (usually bad) as they have direct effects on the running of the computer, or on the interpreted pattern of the rebuilt files (usually a compressed file will fail to open because of it's own safety checks, however). If it's text, or a raw audio or graphics file, then there may be some briefly noticable corruption (a bit of noise, a coloured stripe, "garbage" characters), then returning seamlessly to normality. A compressed audio/video/graphic file will show momentary and usually "catastrophic" distortion even with a couple of bits out of place, which may have knock-on effects for several seconds / lines of the image depending on the exact codec. A MS Word file will be unreadable in word, usually, but you should be able to extract the core text with some ingenuity.

And then bin the disc and start over as it's never really going to get better no matter how many miracle cures you try.

Answer 2

The life span of a written disc depends upon a number of factors including such things as the intrinsic properties of the materials used in the disc’s construction, its manufactured quality, how well it is recorded and its physical handing and storage. As a result, the life span of a recorded disc is extremely difficult to estimate reliably. Since questionable testing and measurement procedures can seriously impact upon and compromise these estimates several international standards have been developed which specify procedures to be used conducting accelerated testing and analyzing the resulting data from prerecorded (pressed) and recordable CDs:

ISO 18921:2002, Imaging materials — Compact discs (CD-ROM) — method for estimating the life expectancy based on the effects of temperature and relative humidity

ISO 18927:2002, Imaging materials — Recordable compact disc systems — method for estimating the life expectancy based on the effects of temperature and relative humidity

For years now many media manufacturers have performed their own lifetime evaluations using these or a variety of other homegrown tests and mathematical modeling techniques. Historically, manufacturers have claimed life-spans ranging from 50 to 200 years for CD-R discs and 20 to 100 years for CD-RW. Be aware, however, that disc producers, manufacturing methods and materials change over time as do applications and cost imperatives.

It is important to remember, however, that nothing lasts forever and that technologies inevitably change. Well-designed products, such as CD-R and CD-RW, allow for seamless transition to the next generation and ultimately, since they embody digital information, contents can be transferred to future storage systems as becomes necessary to preserve whatever has been stored on the discs.

Answer 3

3-4 years or so. It has nothing to do with the filetype, just on the quality of the disk that you bought.

Answer 4

It all depends on how the CD is stored. It recommended that you do NOT touch the surface of the CD, and if it needs cleanign use a link free cloth.

Answer 5

Yes. The "RW" is re-writable. If you wish you can get CD-R's and CD-RW's. The CD-r can only be recorded onto once. The CD-RW can be recorded on & then if you wish you can erase the material on it & re-record on it. Hope this helps.

Answer 6

'bout 15-20 years if kept in optimum condition

Answer 7

They dont, it really all comes down to how well you take care of your dics.