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Guide to Digital Preservation from NIST
Little Hamster writes "The scientists working on the Digital Preservation Program at the National Institute of Standards and Technology (NIST) has released an excellent 50 page guide on care and handling of CDs and DVDs for long term storage. It talks about the effects of light, moisture, radiation, scratches, marking, adhesive labels, and even playback on the discs. For those slashdotters who is not familiar with the physical made up of these optical discs, there is a very nice chapter explaining all the background. And if you only want to know how to care for your precious data, there is a one page summary. And yes, they agreed that glued-on labels are harmful."
The Library of Congress has a guide right here!
1, 1, 2, 3, 5, 8, 13, 21 -- Mathematics is the Language of Nature.
.50 Caliber ammo boxes seem to work best, as far as size. You can conviently fit two CD case holders inside.
Here is the same thing posted anonymously. Mod up this one instead if you feel so strongly about it.
from the 50-page pdf:
Physical mishandling of the disc is usually the cause of polycarbonate*
layer damage. The polycarbonate may also flex or bend if
stored for a long period of time in a nonvertical position.
and
Long-term horizontal storage, particularly in a
heated environment, can cause the disc to become permanently
bowed. While the data may still be intact, the disc may not operate
properly in the drive or permit the laser to follow the track.
*3.1 Polycarbonate (Plastic) Substrate Layer
The polycarbonate substrate makes up most of the disc, including
the area that is read by the laser (opposite the label side on CDs). It
is present on both sides of a DVD, even a "single-sided" disc with a
label on one side. This substrate provides the disc depth necessary
to maintain laser focus on the metal and data layers. It also gives the
disc enough strength to remain flat. Anything in or on the polycarbonate
layer that interferes with the ability of the laser to focus on
the data layer will result in the misreading of data. Accordingly, fingerprints,
smudges, or scratches, as well as such substances as dirt,
dust, solvents, and excessive moisture (which polycarbonate will
absorb), can interfere with the ability of the laser to read the data.
Contact of any foreign material with the polycarbonate substrate
layer should be avoided.
Yes, Sharpies are solvent-based. Look for water-based inks.
Media capacity follows the standard technological growth curve (aka Moore's Law) so that it is both convenient and practical to move your entire library every few years.
Thus my MP3 collection has migrated over time from Jaz cassettes to CDR to large hard disk to DVD.
Apart from the practical aspects of finding a reader for old media, the sheer space taken by old media (e.g. my twenty-odd Jaz cartridges) makes it useful to move regularly.
My MP3 collection, freshly re-created from my original CD collection, fits onto ten data DVDs while it would require about 70 CDRs.
Doing this, while also keeping multiple archives on hard disk (CVS mainly) means I have no problem accessing projects that I worked on 15-20 years ago. No way would I have confidence in diskettes or backup tapes from the same period.
Though I do have a 50cm-wide 150Mb removable Wang disk that has some interesting stuff on it if anyone has an old Wang VS lying around.
Ceci n'est pas une signature
Putting them in a ziplock bag won't do all that much to protect against humidity. You want to put them in a sealed (with vaccum grease) glass or plastic vessel with desiccant, a water-absorbing material. That will keep your stuff cool and dry. They make cabinets that you can just put in your refrigerator.
Not only am I a scientist, I play one on TV
The actually "guide" to care for your DVDs and CDs isn't 50 pages... it's about 2 pages of "do"s and "don't"s. The rest is just technical mumbojumo with the TOC, definition reference, bibliograpy, and other legal stuff at the beginning.
"WOAH 50 PAGES!" Well... yea... but the important stuff is only on a few of them.
So if you plan on printing this out for easy reference... save yourself the extra 48 pages.
You can get free dessicants in a shoe store. There is a small package of silica gel in every box of shoes. Friendly shoe salespeople will be glad to give them to you, since they are normally thrown away.
Putting CDs in a refigerator will work if you put them inside two plastic zipper lock freezer bags, or inside a heavy plastic container. However, use great care when you take them out. Let the entire container warm to room temperature before you open the container. Otherwise the cold plastic will cause moisture condensation.
For those who haven't already seen them, most computer and office supply stores sell markers that are specifically designed for writing on CDs. The last ones I bought were "Smart and Friendly CD Speed Markers", and came in a pack with four different colors.
Silica gel dessicant can also be found/ordered from crafts-supply places; in large (by archival standards) quantities, it's used for drying flowers and the like.
You'd have to construct your own baggies for it.
From the sounds of things you *do* trust a format: your hard disk! What would happen if that died? D'you have and redundancy on this such as RAID-1? If so, what'd happen if you got a virus that wiped everything? Tape/CDR/DVDR archival backups?
Spare disks sometimes count but only if the documents are never going to change and the disk is archived, otherwise there'll always be a "newer version" and it'll most likely be on your primary disk (which may be a point of failure).
Not trying to be pendantic but hard disks are not infallible, I've had plenty die in my time.
As someone who routinley used ammo cases (metal ones- Vietnam era-->late 80's + 90's) for storage of tools, parts, and other vehicle related stuff I've seen a lot of them. Many ammo cases still have a light film of a waxy substance inside (along the corners especially). This waxy film traps water easily (rusty tools...eventual CD degredation). I suspect it can also harbor bacteria, mold, etc.... Not ideal for long term CD/DVD/DAT storage. If you still like ammo cases, check out the *newer* cases for 50 cal. and AR-15 ammo. These are made of a a tough plastic material. And withstand abuse much better.And no waxy film. As a bonus they stack *much* better.....
They may contain solvents, but you're probably safe if there is plastic covering the metal burn layer. If the layer is exposed, do not write on it with a solvent based marker. It may react with the solvent and decompose
Here's a previous post on the same thing
http://slashdot.org/comments.pl?sid=85127&
In answer to your first question; yes it's "real gold" (fake gold, whatever that is, wouldn't have the properties that make gold an appropriate medium for archival purposes).
Of course you're assuming it's a lot of gold, and therefore should cost like gold jewelry. It is a very thin layer, and costs little; it just costs a bit more than a very thin layer of silver or aluminum. You might be getting, say, a dollar's worth (probably much less).
An extra dime or dollar a disk is too much for Wall-Mart's buyers to swallow; you won't see them there.
Resellers whose customers include photographers, research, libraries, content creators, and certain corporate users will stock it.
TY's (as the other posted commented) are reported to be the best CD-R / DVD-R that you can get. You should probably ditch the CD-R format and switch to using DVD-R instead. Mostly due to storage space and having to deal with only 1/7th the number of discs. Best place to get TY media is online (search the alt.video.dvdr newsgroup at google).
In addition you should be looking to add parity/recovery data to your CD-R/DVD-R backup files, which serves two purposes: (a) allows you to verify that the files are still readable and intact (b) allows you to recover damaged files if you have enough recovery data. It allows you to recover from scratches that the underlying ECC was unable to correct for.
The easiest product to use right now is called PAR or PAR2 (I prefer QuickPar). Basically, put all of your files in a single folder (or zip things up into seperate archive files and put those in a single folder) and then use QuickPar to create recovery data. For a CD-R, I usually collect around 650Mb of data together, and then create another 45Mb of recovery data. For DVD-R, I do 4Gb of data and 0.35Gb of recovery data.
Wolde you bothe eate your cake, and have your cake?
Normally punch cards are punched with machines that actually cut the chad right out of the card and push it into a waste bend. You don't get hanging chad with that. You might drop the card deck, lose cards, etc., but as long as you keep them in order, and don't bend, burn, or get them wet this kind will read back properly every time.
That's if you keep the card reader working right - at the college computer center where I worked in 1972, a repairman had to come in and basically rebuild the card reader once a week, or it would start chewing up the cards and spitting the mangled pieces out on the floor. I'm guessing that was a few hundred thousand cards read between repair calls. At 80 bytes per card, it was a fair amount of data in those days, but not much by modern standards. This was an NCR card reader. I think IBM makes much better ones - but you'd still need a lot of punch and reader maintenance and a truckload of cards to back up a 10Gig hard drive. If you really want to use punched media for long term data storage, paper tape might be a better bet. It's more compact, it stays in order by itself, and the machines are simpler and therefore more reliable. And you can use mylar tape instead of paper, if it will last longer.
The other kind of punchcard, used in election systems, is pre-punched to leave each chad hanging by 4 threads of paper. The voters are supposed to push the chad out with a hand-tool. In 1972, the local electric company (or something like that) was using cards like this that the meter readers punched by hand as they read the meters. That computer center had a contract to process this data, but we hated those cards. Even though the users were trained (unlike voters) in how to be sure the chad was punched clean out and not left stuck to the card, you got little bits of paper fiber coming loose and clogging up the machinery. You also got chads that hadn't been punched breaking loose or swinging sometimes, so if you ran the deck through again it would read a few more holes, with maybe one or two of the old holes covered up now.
So there were three issues in Florida. One was that quite simply this was a system with an acknowledged read-error rate around 2% even under the best circumstances. In a recount you'd get a different count every time you ran the cards through again. This had been known for decades, but no one cared until they got an election so close that it mattered.
Second, voters were not trained in using the hand-punch sticks, and the flexible backing that is supposed to support the card while you punch it may have been worn-out or misaligned in some cases so they couldn't get a clean punch on the first try. Someone who understood the system would have checked the backside of the card and pulled off any hanging chad, but with a bunch of octogenarians that have never even programmed their VCR...
Third, Palm Beach in particular had a badly designed ballot. They should have known this, because in 1996 a similar butterfly ballot apparently cost Dole 19,000 votes. It wasn't enough to change the results of that election, and the Dems that run Palm Beach didn't learn anything from it because only Repubs were hurt. (I generally love it when the Demoncrats shoot themselves in the foot, but not when they make a joke out of the most fundamental underpinnings of our republic...)
See Ask Tog's article on this.
NIST tells us not to use anything solvent-based, and Sharpies are solvent-based markers. In fact, the Sharpie Materials Safety Data Sheet (pdf) tells us they contain 3 different solvents - a propanol, a butanol, and an alcohol. One Eric Teel of Jefferson public radio (in Oregon) wrote the manufacturer of Sharpies and they said there could be problems.
Damn, and I've got hundreds of CD-Rs written on with Sharpies. I hope they last till I get around to buying a DVD burner and transferring the data.