CD/DVD longevity

I've read somewhere that CDs/DVDs that have their fixed data "stored" during manufacture last a lot longer than writable cds/dvds.

I've also read many years ago that CDs have been found unsuitable for museum/historic record archiving.

A serried array of servers all equipped with terabyte SSDs or hard drives, all checking their archives with each other.

I have data going back to the 90s, on disks that are less than a year old. Just build your servers and backup up to several

And as each technology becomes obsolete, back up to the next fashionable one

Today in a marine environment Id pick an SSD. IN an airtight box with just a cable coming out

When my data started to get into the multi- gigabyte region I looked for some sort of backup. DVDs weren't big enough, and they died. I ended up with more hard drives. Now while you could have USB drives I opted for 24x7 powered on drives. I am slowly building a raspberry PI machine that will replace the intel PC and spinning rust with an ARM chip and twin SSDs.

I honestly cant think of a better option

Actually the discussion started about whether to buy DVDs (which we do) or just have a spotify etc sub that you pay for monthly aand stream the stuff as you want. The BiL said that's what all the kiddies do these days, they don't and won't own a DVD player or other hardware and all their data/pix/etc is in the cloud. Which is another thing you'd need a sub for. Along with the phone.

(that is, the discussion didn't touch on the best way to back up the desktop)

I said we like the DVDs as then we're not relying on the Internet being there or even off-site power if we've got some backup. That then led on to media and longevity.

I have 20 year old CDs that are 100% fine (I have tested them, and there are quite a lot). There are some that are 18 years old that have a consistent misread in one place, and that was traced to a buffering bug in a particular version of the writer software. I have newer DVDs (probably

These days, I sacrifice some of the space for ECC data. I have tested recovery from a DVD that I butchered with a Swiss Army knife, and got back

The above are archive snapshots of things.

I keep copies of important stuff on tarsnap, which is cheap and convenient as it compresses and deduplicates, and the costs 25 cents per GB/month.

I also have about a terabyte (so far) of archived data in AWS Deep Archive, which costs about $3 a month.

Pre-recorded CDs are made by stamping a master into a metal foil to create indentations which reflect the reading laser differently to the unstamped base, thereby storing 0 and 1 bits (though they encode the data in a way that gives greater resilience to errors, so the 0s and 1s on the CD don't directly correspond to the 0s and 1 in the data). The foil is then encased in plastic. I was surprised that the master stamped the foil, in the same way that a metal master stamps a vinyl record, because I never thought that it would allow such fine detail to be reproduced.

Home-recordable CDs use a laser to burn the pits into metal foil which is already sandwiched between the two plastic layers. That may have a similar life to pre-recorded discs.

But erasable/re-recordable discs uses dyes, and it is those which may have fairly short lives.

I used to backup documents, emails etc to erasable CD every week, back in the days when a backup would fit on a 660 MB CD. I wonder if I still have any of those, dating back maybe 25 years at oldest, and whether any of those discs are still readable despite being kept in non-ideal conditions - I tended to keep the CDs in my car (there was nothing confidential) because I didn't have a garage or other outhouse and I didn't want the backup to be lost in the same fire than killed the computer (assuming the worst!). So those CDs will have been subjected to high temperatures (maybe up to 40 deg C) in summer and sub-zero temperatures in winter, which probably shortens the life of the data remaining readable. I never had a disc go bad, but then I was erasing and rewriting the data every week, so the only thing to go bad was when a disc could no longer be erased and rewritten, which would be detected at writing time, not if the backup was every needed "in anger".

Example of playing a highly damaged CD

I remember the first time I heard a CD. A group of us from university had gone to a hi-fi shop in town for a demo. The salesman proved the greater dynamic range and the negligible background noise, and the total absence of dust and scratch noise.

He then talked out the resilience to scratches, and he got out a very battered CD and scratched it with a sewing needle. The disc played perfectly despite looking as if it had been scuffed and scratched and sandpapered.

My mate, who was a big burly Mancunian with a "don't mess with me, pal" build, said "Giz it here" and he gouged a huge trench in the disc from centre to rim. The salesman turned pale and with some trepidation he played it. The disc skipped a few times but mostly it played OK.

"Now I'm *really* impressed," said my mate. "Do that to an LP and you'd rip the F-ing needle off!"

I've since learned that if you want to really test the error correction, you should make a circumferential scratch which takes out a lot of consecutive samples, rather than a radial one which takes out lots of widely-spaced samples which can be corrected (or at least muted) by reference to the adjacent intact samples.

One number in here, gives M-DISC a 100 year rating. It cannot last longer than the polycarbonate in it. The original "marketing" estimate was 1000 years, but I didn't like that number, because that is as long as Bezos clock.

There are also some archival discs with gold inside the sandwich. Such a contraption, might last longer than diazo dye. Those have existed as media, for a while, but they're only "popular" now in a sense, because we're running out of blanks of other materials. Verbatim has an out-sized control of the market now. Even the jewel boxes, they bought the company that used to make jewel boxes, and now the jewel boxes are Verbatim branded.

Verbatim UltraLife Gold DVD-R up to 100 years [with a tail wind and downhill]

Ritek, it's hard to say whether they're still in business. They used to be the OEM for a large number of other brand names (Fujitsu, Maxell, likely Verbatim, and so on).

The last Ritek I saw in person, somebody took a hundred blank discs, and wrapped them in Saran wrap, then used tape to affix the word "Ritek" to the outside of the Saran wrap. One of the most unhygienic packaging exercises I've ever seen for media. I'm sure none of the staff at Ritek knew their product was being packaged like that. They couldn't even find a few cake boxes somewhere, to avoid doing that ? And after that, there was no more Ritek.

When I bought some Philips (which is "just a brand name" and the name means nothing now), those were CMC discs. And not very nice ones, either. They were hard on the writer, as if the laser was running full blast to burn them. The Ritek I used to get, didn't have that effect on the drive.

The last optical drive I got, the DVD access time was pretty bad. The mechanism was a joke.

Things are going in a predictable direction, that's for sure. If you're archiving something today, it's stone tablets and chisel, for the win.

Paul

Lifetime guarantee?

Lasts 100 or 1000 years or if it fails in 100 or 1000 years it will be replaced free of charge under the warranty, assuming that the manufacturer is still in existence and the product is still being made?

As you indicate, CD/DVD players are becoming less popular and give it 10 years and there may no longer be any manufacturers of the mass produced equipment to play CDs or DVDs. How are the archivists going to access the data on these CD/DVDs in 100 or 1000 years' time, and during the intervening time when they have to check that the data is not being corrupted.

With the "green" revolution and the move against plastics the last two music CDs I purchased came only in cardboard outer sleeves.

I think you'll find 40°C is a bit conservative. Many years ago I had an LCD thermometer with max-min memory in my car. One hot summer's day I got in to find it searingly hot inside and the thermometer display blank. When it cooled down and came back on I pressed the "Max" button to find the inside of the car had reached 61.7°C!

It's also the rate at which the temperature changes, too fast and the CD can warp stressing the recording layer. On a nice sunny day get out of the car where you have had the AC on and come back 10 minutes later to find that you can now fry an egg on the dash :)

Ha! I finally got around to assembling a small garden rotavator my sister bought and shelved 30 years ago. The instructions are on tape! Who still has a player for those?

I can play cassettes and also 1/4" tape. You never know when the facilty might be needed.

Conversely, others are reverting to storing their own data because cloud storage retrieval has become faulty, been removed or was free & now requires payment.

You think it was done for 'green' reasons. I'd bet it was done for cost savings & to maximize profits.

As I sit I have a bookcase full of CDs and DVDs behind me, and to my right a server 2x 2TB disks, with every single one of them ripped into digital form so I can play it anywhere I happen to be.

Including when I am away from home in hospital, which has happened rather too often recently.

Yes.

Since I have been doing 3D printing, I have been thinking about a few bits and bobs for the car - like a smartphone bracket.

PLA is the goto cheap simple plastic for 3D printing but the opinion is unanimous that it simply will deform in in-car usage. You need ABS or ASA apparently. At least 60°C is par for the course for cars in any kind of sunlight.

In really hot climates you can get over 100°C...

There was a rash of disintegrating Range Rover dashboard tops - dunno what that bit between the windscreen and the dashboard top is called - some years back.

I've got an almost brand new one in the loft. From the 80s. Hardly been used. I transcribed loads of vinyl onto cassette for my car.

Happy days!