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| 5/24 |
| 2006/1/11-13 [Computer/HW/Drives] UID:41350 Activity:very high |
1/11 http://news.yahoo.com/s/pcworld/20060110/tc_pcworld/124312 Why I don't backup anything on CDs and DVDs \_ http://www.cdrfaq.org/faq07.html#S7-5. -tom \_ I recently restored a lot of data from 9 track tapes that was between 15 and 30 years old. Much of it was no longer readable and much of what was readable was readable just once. The tape starts to crumble. These tapes were stored in a climate controlled environment, many in the dark. Don't expect more than 20 years with any media. \_ The scrolls of the Chinese civilization lasted over 2000 years. The writings of the Egyptians lasted over 3000 years. Our latest and greatest storage last less than 30 years. Boy, have we progressed a lot or what? I guess the good thing about losing contents is that most of the stuff people store and put on the web is mostly trash anyways. \_ You forgot clay tablets. \_ This isn't really fair; for one thing, Egyptian writings, which were mostly on papyrus, have almost all been lost. For another, the CDs will not be really unreadable even if they degrade; you just won't be able to stick them in a PC and have it read them. Most of the information will still survive. -tom \_ Not to mention the sheer quantity of data on a CD and how much that costs as opposed to hiring some monks to transcribe your source code and binary data files into illuminated texts and then data entry people to later enter that back into a computer when needed. \_ Most of the information we produce is crap anyway, so it doesn't matter if it degrades. When storing written information was hard and required monks or stone masons, only information worth recording (to them) would be saved. We could lose almost all information recorded in digital format (cd, HD, tape, whatever) today and most people wouldn't notice the loss a year later. We'd just make more garbage data. \_ You sound bitter and angry, but....I'm honestly not sure what you're bitter and angry about. \_ There is no "sound" in text. I'm not bitter about crap data which is why you can't figure out what I'm bitter about. I'm not bitter. That makes no sense. It's simply the case IMO that most data is crap and of no use to anyone and wouldn't be missed if it vanished forever because we as a society produce so much crap data to begin with. Honesty is not anger nor bitterness. \_ Honestly, you sound bitter and angry. \_ Have you never taken a high school literature class? The "sound" in text is called tone, and I agree with op that you did sound bitter and angry. -!op \_ *laugh* ok, yes, you're right, you caught me i am deeply bitter and angry about all the junk data we produce. sheesh, weirdos. \_ Hmm. Now you just sound like an asshole. \_ You seem really upset over such a trivial thing. And it's kind of weird that I'm the asshole yet you're the one tossing names around. whatever. \_ Heh, okay, fair enough. I am being pretty damned silly. My apologies, sir! \_ I have a book on the shelf at home that was still completely readable, and it was printed in the 60s before I was born. :-) \_ http://en.wikipedia.org/wiki/CD-R Cyanine dye = several yeanrs Cyanine dye = several years (earlier versions) Azo = decades Phthalocyanine = hundreds of years German IBM guy needs to get with the program: "Many of the cheap burnable CDs available at discount stores have a life span of around two years. Some of the better-quality discs offer a longer life span, of a maximum of five years." "Some of the better-quality discs offer a longer life span, of a maximum of five years." WRONG WRONG WRONG! \_ Few people realize how big a market microfilm/microfiche are; most big banks & corporations store customer and transaction records on multiple copies of these. -John \_ Not big enough for Kodak to live off it. \_ That part of Kodak does, however, seem to make money. -John |
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| news.yahoo.com/s/pcworld/20060110/tc_pcworld/124312 John Blau, IDG News Service Tue Jan 10, 8:00 AM ET Opinions vary on how to preserve data on digital storage media, such as optical CDs and DVDs. Kurt Gerecke, a physicist and storage expert at IBM Deutschland, has his own view: If you want to avoid having to burn new CDs every few years, use magnetic tapes to store all your pictures, videos and songs for a lifetime. Click Here "Unlike pressed original CDs, burned CDs have a relatively short life span of between two to five years, depending on the quality of the CD," Gerecke says. "There are a few things you can do to extend the life of a burned CD, like keeping the disc in a cool, dark space, but not a whole lot more." CD-R and CD-RW, have a recording surface consisting of a layer of dye that can be modified by heat to store data. The degradation process can result in the data "shifting" on the surface and thus becoming unreadable to the laser beam. "Many of the cheap burnable CDs available at discount stores have a life span of around two years," Gerecke says. "Some of the better-quality discs offer a longer life span, of a maximum of five years." Distinguishing high-quality burnable CDs from low-quality discs is difficult, he says, because few vendors use life span as a selling point. Similar Limitations Hard-drive disks also have their limitations, according to Gerecke. hard drives, he says, is not so much the disk itself as it is the disk bearing, which has a positioning function similar to a ball bearing. "If the hard drive uses an inexpensive disk bearing, that bearing will wear out faster than a more expensive one," he says. His recommendation: a hard-drive disk with 7200 revolutions per minute. To overcome the preservation limitations of burnable CDs, Gerecke suggests using magnetic tapes, which, he claims, can have a life span of 30 years to 100 years, depending on their quality. "Even if magnetic tapes are also subject to degradation, they're still the superior storage media," he says. But he's quick to point out that no storage medium lasts forever and, consequently, consumers and business alike need to have a migration plan to new storage technologies. "Companies, in particular, need to be constantly looking at new storage technologies and have an archiving strategy that allows them to automatically migrate to new technologies," he says. And for those sitting on terabytes of crucial data, that could be a colossal problem." High-Quality Magnetic Tapes Visit our site for all your home, office and industrial tape needs. We have over 60 different types of tapes like cloth, foam, kapton, hazard tapes and more. |
| www.cdrfaq.org/faq07.html#S7-5 The dye types currently in use are: * cyanine dye, which is cyan blue in color (hence the name); In addition, Kodak has patented a "formazan" dye, which is light green. This has been reported to be a hybrid of cyanine and phthalocyanine. The reflective layer is either a silver alloy, the exact composition of which is proprietary, or 24K gold. Aluminum isn't used in CD-R media because the metal reacts with the dyes. The color you see is determined by the color of the reflective layer (gold or silver) and the color of the dye (light blue, dark blue, green, or colorless). For example, combining a gold reflective layer with cyanine (blue) dye results in a disc that is gold on the label side and green on the writing side. Many people have jumped to the conclusion that "silver" discs are made with pure silver, and have attempted to speculate on the relative reflectivity and lifespan of the media based on that assumption. According to one source, silver is susceptible to corrosion when exposed to sulfur dioxide (a common air pollutant), so manufacturers use alloys of silver to inhibit corrosion. Taiyo Yuden produced the original gold/green CDs, which were used during the development of CD-R standards. Mitsui Toatsu Chemicals invented the process for gold/gold CDs. Mitsubishi's NCC subsidiary developed the metalized azo dye. Silver/blue CD-Rs, manufactured with a process patented by Verbatim, first became widely available in 1996. According to the Ricoh web site, the silver/silver "Platinum" discs, based on "advanced phthalocyanine dye", were introduced by them in 1997. They didn't really appear on the market until mid-1998 though. One reason why there are multiple formulations is that the materials and processes for each are patented. If a new vendor wants to get into the CD-R market, they have to come up with a new combination of materials that conforms to the Orange Book specifications. Some CDs have an extra coating (eg Kodak's "Infoguard") that makes the CD more scratch-resistant, but doesn't affect the way information is stored. The top (label) side of the CD is the part to be most concerned about, since that's where the data lives, and it's easy to damage on a CD-R. Applying a full circular CD label will help prevent scratches. There are four factors to consider: 1 Does it work with your recorder? Some audio CD players (like the ones you'd find in a car stereo) have worked successfully with one brand of media but not another. There's no "best" kind, other than what works the best for you. Some people have found brand X CD-R units work well with media type Y, while other people with the same unit have had different results. Recording a disc at 4x may make it unreadable on some drives, even though a disc recorded at 2x on the same drive works fine. To top it all off, someone observed that discs burned with one brand of CD-R weren't readable in cheap CD-ROM drives, even though the same kind of media burned in a different device worked fine. The performance of any piece of media is always a combination of the disc, the drive that recorded it, and the drive that reads it. A number of specific discoveries have been posted to Usenet, but none of them are conclusive. Many people have reported that Kenwood CD players don't deal with CD-Rs very well, while Alpine units play nearly everything. However, things change as product lines evolve over time. Some users have found that the *quality* of audio recordings can vary depending on the media. Whatever the case, if you find that CD-Rs don't sound as good as the originals, it's worthwhile to try a different kind of media or a different player. One final comment: while there are clearly defined standards for CD-R media, there are no such standards for CD and CD-ROM drives -- other than that they be able to read CDs. It is possible for media to be within allowed tolerances, but be unreadable by a CD-ROM drive that can handle pressed discs without trouble. All you can do in this sort of situation is find a better-quality CD or CD-ROM drive, or switch to a brand of media whose characteristics are on the other side of the tolerance zone. They are now manufactured by TDK, Ricoh, Kodak, and probably several others as well. Mitsui Toatsu Chemicals (MTC) made the first "gold" CDs. They are now manufactured by Kodak and possibly others as well. Most CD-R brands (eg Yamaha and Sony) are actually made by a handful of major disc manufacturers. Attempting to keep track of who makes what is a difficult proposition at best, since new manufacturing plants are being built, and resellers can switch vendors. You can't tell how well a disc will work just by looking at it; the only way to know is to put it in *your* recorder, write a disc, then put it in *your* reader and try it. Statements to the effect that "dark green" is better than "light green" are absurd. Some discs are more translucent than others, but that doesn't matter: they only have to reflect light in the 780nm wavelength, not the entire visible spectrum. section (3-31) for some other remarks about recording speed. Speed considerations are more important for CD-RW than CD-R. Many drives refuse to record at speeds higher than the disc is rated for. On top of that, there are "ultra speed +" blanks (for 32x recording), "ultra speed" blanks (for 8x-24x), "high speed" blanks (for 4x-10x) and "standard" blanks (for 1x-4x). The faster blanks are labeled with a "High Speed CD-RW" or "Ultra Speed CD-RW" logo, and will not work in older drives. The Orange Book standard was written based on the original "green" cyanine discs from Taiyo Yuden. Cyanine dye is more forgiving of marginal read/write power variations than "gold" phthalocyanine dye, making them easier to read on some drives. On the other hand, phthalocyanine is less sensitive to sunlight and UV radiation, suggesting that they would last longer under adverse conditions. Manufacturers of phthalocyanine-based media claim it has a longer lifespan and will work better in higher speed recording than cyanine discs. html for some notes on low-level differences between media types. There is no advantage to using expensive "audio CD-Rs" or "music blanks". There is no difference in quality between consumer audio blanks and standard blanks from a given manufacturer. If you have a consumer audio CD recorder, you simply have no other choice. There is no way to "convert" a standard blank into a consumer audio blank. section (5-12) for notes on how you can trick certain recorders into accepting standard blanks. Trying samples of blanks is strongly recommended before you make a major purchase. Remember to try them in your reader as well as your writer; they may not be so useful if you can't read them in your normal CD-ROM drive. Maxell's CD-R media earned a miserable reputation on Usenet. In April '97 Maxell announced reformulated media that seemed to work better than the previous ones. Brands most often recommended: Mitsui, Kodak, Taiyo Yuden, and TDK. It appears that HP, Philips, Sony, Yamaha, and Fuji use these manufacturers for most of their disks. Sometimes a particular line of discs from a particular manufacturer or reseller will be better than others from the same company. For example, Verbatim DataLifePlus discs are recognized as pretty good, but Verbatim ValuLife are seen as being of much lower quality. For example, in June 2003 Mitsui Advanced Media was purchased from Mitsui Chemicals by Computer Support Italcard (CSI) of Italy to form MAM-A, Inc. Some manufacturers maintain plants in different countries, and don't always maintain the same level of quality. In humid tropical climates, care must be taken to find discs that stand up to the weather. One user reported that the data layer on Sony CDQ 74CN discs began cracking after a couple of months in an otherwise sheltered environment (eg no direct sunlight). Mitsubishi CD-R 700 and Melody 80 Platinum discs fared much better. In general, CD-RW media isn't recommended for long-term backups or archives of valuable data. The manufacturers claim 75 years (cyanine dye, used in "green" discs), 100 years (phthalocyanine dye, used in "gold" discs), or even 200 years ("adva... |
| en.wikipedia.org/wiki/CD-R The Orange Book consists of several parts, furnishing details of the CD-WO, CD-MO (Magneto-Optic), and CD-RW (ReWritable). The latest editions have abandoned the use of the term "CD-WO" in favor of "CD-R". A blank CD-R is not "empty", it has a pregroove with a wobble (the ATIP), which helps the writing laser stay on track and is used to ensure the data is written to the disc at a constant rate. As well as providing timing information, the ATIP (absolute time in pregroove) is also a data track containing information about the CD-R manufacturer, the dye used and media information (disc length etc). The pregroove is not destroyed when the data is written to the CD-R, many copy protections use this to easily distinguish a copy from the original CD. The improvements were mainly due to optimisation of special dye compositions for CD-R, groove geometry, and the dye coating process. Low-speed burning at 1x is still used for special "audio CD-Rs", since CD-R audio recorders were standardized to this recording speed. Unfortunately, many manufacturers add additional coloring to disguise their cyanine CD-Rs, so you cannot determine the formulation of a disc based purely on its color. Similarly, a gold reflective layer does not guarantee use of phthalocyanine dye. edit Writing methods The blank disc has a pre-groove track onto which the data is written. The pre-groove track, which also contains timing information, ensures that the recorder follows the same spiral path as a conventional CD. Instead of pressing a CD with indentations, a CD-R writes data to a disc by using its lasers to physically "burn" the organic dye. When heated beyond a certain temperature, the area that was "burned" becomes opaque and reflects less light than the areas that have not been "burned". Note that the "burning" process does not produce the conventional indentations (pits). The reflection modulation can be detected by a photo-diode. Upon reading back the stored information, the laser operates at a low enough power not to "burn" the dye and an optical pick-up records the changes in the intensity of the reflected laser radiation when scanning along the groove and over the pits. The change of the intensity of the reflected laser radiation is transformed into an electrical signal, from which the digital information is recovered ("decoded"). The decomposition of the dye in the pit area through the heat of the laser is irreversible (permanent). Disc At Once - the whole CD-R is written in one session with no gaps and the disc is "closed" meaning no more data can be added and the CD-R effectively becomes a standard read-only CD. With no gaps between the tracks the Disc At Once format is useful for "live" audio recordings. Track At Once - data is written to the CD-R one track at a time but the CD is left "open" for further recording at a later stage. It also allows data and audio to reside on the same CD-R. Packet Writing - used to record data to a CD-R in packets allowing extra information to be appended to a disc at a later time or information on the disc can be made "invisible". In this way CD-R can emulate CD-RW however each time information on the disc is altered more data has to be written to the disc. There can be compatibility issues with this format and some CD drives. A rough estimation of the amount of data on a CD-R can be gained by inspecting the playback side of the disc. accelerated aging tests as the technology has not been in existence long enough to verify the upper range. With proper care it is thought that CD-Rs should be readable one thousand times or more and have a shelf life of several hundred years. Unfortunately, some common practices can reduce shelf life to only one or two years. Therefore, it is important to handle and store CD-Rs properly if you wish to read them more than a year or so later. Optical discs commonly used for burning, such CD-R and CD-RW have a recording surface consisting of a layer of dye that can be modified by heat to store data. The degradation process can result in the data "shifting" on the surface and thus becoming unreadable to the laser beam. Many of the cheap burnable CDs available at discount stores have a life span of around two years,Some of the better-quality discs offer a longer life span, of a maximum of five years. Distinguishing high-quality burnable CDs from low-quality discs is difficult, because few vendors use life span as a selling point. Recommended care and storage practices for CD-Rs include: * Store vertically in jewel cases or slim-line cases, one disc to a spindle. Archival cases use a ridged ring which grip the disc and prevent the recording surface from touching the surface of the case. To remove a CD-R from a jewel case, press down on the hub while gently gripping the edges of the disc; you should be able to simply lift the disk out of the case. Try to avoid getting fingperprints on the data side of the disc. toluene based and should never be used to label optical media. Many vendors sell marking pens which are safe to use to label optical storage media. Over time, solvents in the paper, adhesives and inks can all degrade the disc. Perhaps counterintuitively even minor scratches on the label side can damage a disc, as the layer of plastic between it and the reflective layer is much thinner there. error-correcting codes, minor scratches on the data side should not render the disc unreadable, unless there are many of them close together. Deep scratches on the data side can interfere with the focus of the laser and render a disc unreadable. Scratches from rim to center are less harmful than concentric circular scratches. edit Cleaning CD-Rs As a general rule only clean a CD-R if the playback is affected. The error correction of CD-R can effectively read through fingerprints as well as a highly scratched information surface. Excess dust can be removed from the information surface by very lightly wiping the information side with a very soft cloth (such as a reading glasses cleaning cloth) from the centre of the disc in an outwards direction. Never wipe the information surface of any type of CD in in circular motion around the centre as this may create scratches in the same direction as the information and potentially cause data loss. An even gentler method is to blow the dust away using a can of pressurized clean air. gasoline) or any other type of petroleum-based solvent to clean a CD-R. Use of petroleum based solvents will damage the polycarbonate surface and the CD-R will become unreadable. edit Readability in CD drives There was some incompatibility with CD-Rs and older CD-ROM drives. This was primarily due to the lower reflectivity of the CD-R disc. In general, CD-ROM drives marked as 8x or greater will read CD-R discs. |