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CD-R Lifespan - Is It The Label?
sysadmn writes "Slashdot has discussed archival lifespan of CD-R media before. Fred Langa revisits the issue with a new twist: Are glue-on labels causing premature failure? Much more common than rain forest fungus! From Fred's informative LangaList newsletter."
...but I've stopped doing that. For one thing, humidity causes the clue to come off, leaving you with a bubbly cd that doesn't fit in many slot cd players (esp. car players). Dragging the label off at this point will damage the cd.
Commercial manufacturers silkscreen their CDs, they don't use adhesive labels.
All media degrades. The trick is to use redundant data, and re-copy it before the media is expected to fail.
Kodak used to subject their CDs to "torture tests" to see how they'd stand up. Their "Gold Ultima" CDs were reported to have a 100-year archival life. Now, they're saying the same thing about the Ultima brand (now that the Gold brand is discontinued). Study results are here.
:-)
All I can say is that Kodak seems to have done a lot worse to their CDs than your friend did with just his tongue.
D.
I have noticed that on some of my CDR's, burning slower results in a different color than a faster burn. I guess the dye is being changed more when it is slower. So now, for CD's that I want to keep for a few years, I write them at 4x even though I have a 48x burner. As for the labels, I don't use them.
It's only anecdotal evidence, but the only CDs I have that have lasted more than 19 months or so are my Kodak Golds, the oldest of which were burned sometime in 1995. In particular, I've found any CDs that use a blue dye to be the most fragile/short-lived. However, I do live in a location with fairly high humidity (Brisbane, Oz).
but i have learnt a few things!
- don't let cdrs touch each other ever. they *will* scratch each others data off. never put written cdrs on spindels or two to a slot in a case. i was too cheap to buy another case and immediately b*gg*r*d some of my discs stickin em two to a slot w/ a grain of sand in between!
- if you have to put a cd down not in a case, put it play side down. i've seen people put them label suide down thinking its 'protecting the disc' - worst thing you can do. a scratch on the plastic side ain't so serious, you could maybe polish it out in a pinch
- overprints are good, if you can get them. these are discs where the original label was printed wrong and has been.. overprinted. = cheaper AND tougher in my experience :)
- writing on a disc with soft tip permanent marker (you dont have to buy "cd markers", thats a joke) has never caused me a problem. i think labels are asking for trouble, but ive always been too cheap to try them :p don't use a hard tipped thing eh in case anyone is stupid to try a biro or sommat
- some cds are just sh*t and fall apart no matter what you do! if data is really vital i'd get two stacks of diff. makes of media and burn two sets (of course, im never sensible enough to do this)
- use the verify funtion of your cdr app if you're not in a hurry. then you know at least the disc started out alright.
there's probably loads more things i'll think of after posting this eh.
the biggest problem i have is with some cds developing mysterious "spots". there is a little speck with a discoloured ring around it, that can fall off, but even if it doesnt the disc is ruined. anyone have any idea what it might be that's touching my discs and doing this to them? i'd love to know, 'cos im stumped. id post a picture of one of these if i was somewhere with a scanner.
oh yeah, did i mention i was cheap! :p maybe buying more expensive blanks would help some of my problems, but i suspect you don't get what you pay for necessarily.
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Parchment can last longer than that if you take proper care of it. You might need to design a special printer to use it. My suggestion would be to have thousands of monks make copies of your data.
My only political goal is to see to it that no political party achieves its goals.
What is an acceptable digital archival media?
All media degrades. The trick is to use redundant data, and re-copy it before the media is expected to fail.
And don't forget to store archival media in an archive. That's right; cool (doesn't have to be freezing, but a consistent not-warm temperature), dark, low humidity.
Non-damp basements spring to mind (as long as you don't have heating equipment in there).
You might consider sealing off CD-R media in an airtight container, such as a (zip-lock) plastic baggy of suitable quality. If it's an opaque one that locks out light as well, all the better.
If you're in the archive (basement) and need light, take care not to hit your archive media with direct light, and take care that UV light is kept to a minimum (i.e. fluorescent lighting is usually better than incandescent lighting).
It also helps to use standard 650MB CD-R media with the ISO 9660 filesystem, in stead of the latest and greatest 818 MB overburned FooFS combination.
Don't burn at 52 speed. Use media that is specced for the lowest speed you can find, and burn it at that speed or lower. You need to drink coffee anyway.
Consider tape backups. Consider a regular archiving/back-up cycle, so that if a piece of media is a dud, you'll have a duplicate from the week before or after.
Store media before use under the same conditions as you would the written archival piece. Don't buy from stores that have humid, warm warehouses.
Index and catalogue your archive. Not only will it make it easier to find things, it will also help to find or sort out duplicates - handy if you switch to a different media and re-archive your old CD-Rs on DVD for example. Archive the index as well.
Use integrity checks, such as checksums. Use compression formats that are easy to fix if a few bits go bad (e.g. no spanning ZIP archives which are useless if the last disk goes missing).
Mix lots of media, unless you're sure that what you've got is a high quality. That way, if wednesday's backup is a dud because of crappy media, the backup from tuesday might at least be better.
Once in a time, randomly check media to see that it's still readable.
Another poster asked about CD-R based RAID; you can just use PAR files (of USENET fame).
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