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NIST Releases Study Of CD/DVD Longevity
dirkin writes "The National Institute of Standards and Technology has released a preliminary study of the potential lifespan of CD-Rs and DVD-Rs. The PDF study is here. A good starting point for deciding what type of media to purchase to keep those backups and photos kicking around longer. (You DID buy the silver/gold alloy phthalocyanine CDs, didn't you?)"
the speed in which the CDR is burned sometimes it makes a difference, for the highest reliability I think 1x is the best.
Just backup to harddrives.
I'm using Araid99-1000 units in my computers, and backup is just replacing the slave drive (even while the computer is on and running).
The price for say, WD120mb drives are so cheap now that it is probably close to the cheapest, safest and most accessable backup format available.
Just do what I do : buy a rack, install in front of your machine (under the DVD or CD-RW or somewhere) and back up all your important data (or your entire harddrive) to a separate harddisk. Prices on smaller models (40-60 gigs) aren't all that steep, and most people I know have trouble just filling up their 'small' 20 or 30 gig drives. A spare 60 gigger rackdisk will keep you satifsied for a long time... Alternatively you could also just buy an external fire-wire or USB harddisk, although I don't really have all that much experience with those kind of devices.
Simply buy twice the number of drives you need, and do an rsync between the two sets now and again. For added safety, get a friend with broadband and store the second box there. Then you are safe from fire, theft, drive crashes etc, with minimal effort to keep the backup up to date.
I've got a whole load of burned CD's that I created up to about 5 years ago.. and on varying quality of media, and a lot of them aren't any problem.
I suppose storage is the key thing, keep them in a dark cool place will help them last just that bit longer (unless you have a case of those little bugs that like eating the data layer).
Although they are of a similar tech, what about DVD recordable disks? I've got plenty of those now... but if I keep doing what i've been doing over the years and backup my backups onto newer media then I'm not too worried.
Just my $0.02
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This article is quite inconclusive in my mind. There is nothing in it that describes the care given to the cds for the past 20 months (what cases, if any, they were in, the amount of light and heat they were exposed to, etc.) Also, there was no mention of the quality of the media they were burned on, nor the speed at which they were burned. Too many variables are introduced in the article to fairly say that cd media is not a viable backup alternative. It seems like decent advice to burn slowly and simply take care of your cds, they would last much longer.
Save it to film.
www.bannination.com Two things float to the top he
Or, rather literally translated into English: "Our sample shows that there is a lot of junk on the market. We have found cd-rs that should never have been for sale. Possibly it concerns rejected batches." Which suggests to me that the correct heading of this article should be: CD-Rs are like everything else: you get what you pay for.
Back in the eighties, when regular CD's were first introduced that could be read by a standard computer (pc, mac, etc), the discs were fairly thick, and consisted of (iirc) from top down:
disc label
protective coating
data layer (usually pressed)
protective coating
Then at the end of the eighties, I don't recall exactly what year, but it was adopted by various cd makers till eventually all, the price of CD's dropped dramatically, almost in half.
The reason for this was the fact that the top protective layer was removed from the manufacturing process, leaving just the thin disc label and it's material to protect the data layer, barely.
I want to clarify that I'm talking about regular PRESSED cd's manufactured in bulk, and not dye layered ones, but the point is the same in both cases. By removing the top protective layer, it allowed manufacturing of CD's to drop in price dramatically.
I'm positive there have been other cost cutting measures used for dye layer CD's that the manufacturers have adopted over the years, such as cheper dyes that are affected faster due to exposure to sunlight, and so on.
It's not just about scratches or dye, but about the overall picture here. The manufacturers WANT to have built in obselesance. This gives them a nice steady flow of income when one has to contually burn his media archive every 2 years.
Food for thought anyhow. I thought I'd post about what I saw in the eighties, in case it was relevant.
user@host$ diff
used to include a study of glove compartment temperature cycles for their high end discs...
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
You DID buy the silver/gold alloy phthalocyanine CDs, didn't you?
No, I've not ever ran across them, and it's not like they print the reflective layer and dye compositions on the side of the package. Mine are always green-ish.
(fp?)
"Alcohol, Tobacco, Firearms, and Explosives" should be a convenience store, not a government agency.
They seem to still be very readable. I don't get all this "only lasts a year or two" crap about CDRs. Obviously this is false.
Meh.
that buying cheap crappy CD-Rs meant that your data died faster, but I had no idea how the degredation worked. What about the "armored" DVD-Rs from places like Datawrite? They're supposedly almost impossible to destroy. How well do they stand up?
I wish they would test the Memorex black cd's. If you scratch the non-readable side of them, they are actually gold. I've been using these for the past year or two. The price is good on them, and I've had no problems.
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The trouble with this approach is the same as the trouble with preserving old videotape material, something I used to be involved in.
;)
I worked for a museum that preserved such materials, and always wanted to establish a program not just to copy older videotape to newer analog formats (which already existed) but to copy and RE-copy those digital tapes on a two-year cyclical program; the digital data wouldn't degrade during the transfer, and by essentially replacing the media containing the data on a regular basis, we'd have a good chance of saving the material long-term.
I never got approval for a simple reason: tape stock is expensive, staff is expensive, and coordination of such an effort requires diligence. Similarly, you could use CD-R/DVD-R to back up your material and re-burn the discs on an ongoing rotation, but most people don't have that kind of discipline even if they have the money.
For me personally, I've found the best approach is to maintain the data on a redundant RAID array, with occasional backup to DVD-R. This way, the data itself will outlive the death of individual local drives, while the DVD-R only needs to serve as a short-term disaster-recovery solution.
Of course, once my critical dataset gets large enough to require more than a few DVD-Rs, I'll probably get lazy...aren't we about due for a new format by now?
So what do i use for backing up data I want to keep for years?
CDr's now "suck".. I just moved alot of data off OLD hd's i had sitting around. They worked fine when i put them away but alot of them failed to spin up or had big time read errors. I thought moving everything to CDr would be the way to go.
I also use a RAID setup on netbsd with a few new seagate drives. Seems to be working fine but a good spike or other big hardware failer could knock the drives out... and just putting one drive away gets me back to my 1st problem.
So what do use?
I have to return some videotapes...
My 18-month old 120GB, 7,200 rpm Maxtor HD packed it in two weeks ago for no particular reason. I have partial backups on CD but stopped backing up several months ago when I found out that the CD's don't last. I was trying to figure out another approach to backup when this happened.
I have used numerous hard drives over the last 12 years and used to replace due to space. More often these days, I replace due to failures.
So the RIAA need not worry - disk drive and CD manufacturers will take care of their little problem by engineering reliability out of their products.
DVD media should do better than CD, if only because the data layer is completely encapsulated, as opposed to covered in thin lacquer like CDRs. This assumes, of course, that the edges are similarly well sealed. Looking at my (DataWrite 8x plain white printable) DVD+Rs, that seems to be the case - the data layer stops about 1mm short of the edge of the disc.
I have a ton of CDr's (everything I've ever created or downloaded) on the theory that when my hard drives go, I'll still have the orginal of whatever was on there. There's way too much to make new copies of, almost a 100 gig.
What's the bottom line? How long can I be sure my CDrs from 1997 will be of any use?
(Man, remember 1x burners?)
Sig not available, please try again later. If the problem persists, then the submitter is an idiot.
DID NOT name this mysterious "D2" sample that was so much better than the others?
While it was not named, I think I can guess. Mitsui/MAM-A. They are stating now that their DVD-Rs are silver/phenothiazine based, which is the same chmistry that kicks serious butt with CD-Rs.
What will be interesting is to see if this chemistry holds up with Blu-Ray. The shorter wavelength may or may not be compatable with the dye.
The reflective layer on CD's is what makes it all work. If you get a cheap CD and look at it's pale green layer... then get a hold of a Kodak ultima CD, you'll certainly spot the difference in reflectivity.
:
:-) as the reader will be unable to discern the difference between "low" from low reflectivity or a "low" from the now-aged dye.
I *presume* that as the media ages, the margin of error slowly shrinks to the point where your media is now unreadable. As all you're reading is either
- the reflected light from the reflective layer
or
- the absence of reflected light due to the dye
Discs with lower reflectivity will end up useless first (all other things being equal... which they're not
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
Uh, my removable media are _harddisks_. I've got my HDDs in caddies/trays (with fans) so I can slide them out easily.
:) ), then store/archive the HDDs.
Doing the figures, HDDs aren't really that expensive compared to other media especially when you factor in the performance, reliability, stability and convenience. Buy one or two 200GB HDDs, backup everything (two or more copies just to be sure
The stability of data on magnetic disks is pretty good. The only problem usually is the electronics failing or the mechanical stuff failing. But if you're not using/abusing the drives, the shelf life is pretty good.
When the time comes to migrate the data off the obsolete 200GB drives so you can still read the data, it's a lot faster and simpler to copy the data off the 200GB drives than it is to copy from other removable media. The transfer rates of optical or tape media are pretty bad. OK DVD stuff isn't that bad, but writing isn't that fast... I personally believe tapes and tape drives are a big con-job nowadays.
It'll be a lot better if hotswap SATA drives and their caddies become common and cheap. Then backing up wouldn't require a power down.
Talk about bad luck on archivals and that one-in-a-billion catastrophic failure... the aerospace company I'm an engineer at lost a good deal of test data for a few aircraft engine performance tests in that (1) a disc in a RAID server failed... I think it must've been RAID-5 or whatever lets one disc crap out... (2) while replacing that disc, multiple other discs failed. The remainder of the RAID array now being worthless, (3) the IT/data company went to pull tape backups, and for much of that data (I think on two separate tape systems) the data was corrupt/useless. I never heard total volume that was irreplaceable and lost (there'd never be enough time OR millions of dollars thrown at it, considering the data spanned *years*), but I'd estimate it's measured in the low TB range.
Don't lump RW in with CDR!
CD-RW uses a phase change crystaline latice to store data, not a volatile organic dye. This means that the chemical breakdown seen in CD-R's is not going to be present in a CD-RW. For this reason I think that CD-RW is a vastly superior archival solution, of course it doesn't work in areas where WORM is mandated (such as securities firms) but for something like home backups it should seriously be considered. Unfortunatly even with the recent flurry of attention to CD-R archival quality (or lack thereof) I still haven't seen even a pseudo-scientific study done on CD-RW disks. Early on there was some flutter about CD-RW having a shorter archival life then CD-R, but back then CD-R manufacturers were claiming 100+ year lifespans, which we know simply isn't true.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
I had a friend tell me his store was bidding on a huge job to convert hundred of boxes of documents to PDF by scanning the documents. They were going to make CD-Rs with the PDFs on them.
They were then going to dispose of the paper documents via shredding.
This is an oil company with 20+ years of records.
The people he was bidding against were basically of the opinion of: "oh, these things last forever. don't worry about it."
Whereas I thought, "I think CD-Rs have a 10 year or so shelf life in darkness with low humidity."
I figured you would some optical character recognition to put into a keyword database and RAID servers and all kinds of good stuff. Not to mention making copies of the copies every X years.
Not to mention the fact that you would wonder if Cd-rom drives and Adobe Acrobat will be around in 10 or 20 years.
I kind of wonder how many people will get bitten by this issue.
I think this has been discussed before on slashdot that due to our digital world, ironically if there was some sort of global catastrophe there would be very little record of our civilization in 100 years.
...but the really annoying thing about CDs/DVDs, is that you have no idea that they have failed. You'll only notice when you try to recover. And I haven't found any program that'll let you burn a RAID - Redundant Array of Inexpensive Discs. If you want additional redundancy, you have to meddle around with creating PAR sets and distributing them yourself.
One small thing, which I've yet to see but maybe some slashdotter can point me to - is there any way, under windows, to automagically mirror a folder on one drive, to another folder (on another drive). I don't mean a full RAID1 of the entire disk, but the few 100mbs that are crucial. Sacrificing 160GB HDD space just for that seems like overkill.
Kjella
Live today, because you never know what tomorrow brings
It was too much of a hassle to find the right one, so I transferred everything to HD. About 10 or so CD's were irrecoverably damaged. Some had faulty areas but were mostly readable.
Nowadays you should just buy a couple of 160+ gig HD's to store this kind of stuff. CD just does not have the capacity or ease of use or longevity, and DVD is not much better.
DVD drives in particular seem to be very picky about what they can read - I have 5 DVD drives only 2 of which read DVD+R's burned with HP NC8000, for example.
'Once scientists, even the dim-witted social scientists, get muzzled, the Western Civilization is finished.' - oldhack
IN Egypt's sandy silence, all alone,
Stands a gigantic Leg, which far off throws
The only shadow that the Desart knows:--
"I am great OZYMANDIAS," saith the stone,
"The King of Kings; this mighty City shows
"The wonders of my hand."-- The City's gone,--
Nought but the Leg remaining to disclose
The site of this forgotten Babylon.
We wonder,--and some Hunter may express
Wonder like ours, when thro' the wilderness
Where London stood, holding the Wolf in chace,
He meets some fragment huge, and stops to guess
What powerful but unrecorded race
Once dwelt in that annihilated place.
-- Horace Smith, Ozymandias, 1818
Slashcode bug: you apparently copied that text from a page that used Microsoft Latin1 encoding, aka CP1252. This allows you to represent the EM dash with 0x97. That shouldn't actually work, since Slashdot advertises its pages as using the ISO version of Latin1, 8859-1, which doesn't use that value. Ironic at site that is so unfriendly to Microsoft. Also interesting that Firefox ignores this inconsistency between a page's advertised and actual encoding.
The correct, vendor neutral way to represent an EM dash on a Latin1 page is to use a character entity (& mdash; or & #8212; space added after the & to get past filter). Slashcode used to allow this, but now removes character entities. Correct encoding is obviously not a high priority!