Life expectancy of flash memory data

[KuroNeko]

This is a general question, unrelated to a specific PPC type, so moderators, if there's a more suitable forum for this hardware question, please feel free to move this. Thx.

I'm trying to find a good backup medium for smaller files, mainly documents, some pictures etc. CDRs and DVDRs that I've tried don't last much longer than 5-10 years. HDs may or may not retain data longer and last longer if they're not in use. But they're expensive - if you lose one you lose a great big heap of data and therefor you'd need backups of backups...

So I'm considering flash now that the prices have come down. Either USB sticks of SD/CF cards. Preferably the cards, to work with my PPC.

The data will be stored on them, then they'd be put in a box. So they would not be in continuous use.

From what I've read, flash memory wears only by writing (or more correctly by prior erasing) and not by reading data. These cards would not be continously rewritten, only written to once and then left alone except for an occasional read.

But what about data retention? How long will data remain intact on a card? Is there some other material degradation that limits the life expectancy?

Any studies that have been done regarding this, similar to CDR/DVDR media?

Neko

[ADBrown]

The short answer is that nobody knows for sure, because flash memory made with modern processes isn't old enough to test properly. However, there is a generally agreed-upon figure, that memory cards will retain their data for at least ten years without being touched. Whether they'll last longer, or if you can simply refresh the card by copying files off it and back on, that I don't know.

[Cybrid]

I guess 01010010101010 written on stone doesn't work to well either... :wink:

Question. What happens to CDs and DVDs if the are kept for further than 5-10 years?
Is the read process slowly damaging them? Couldn't it be simpler to make multiple copies? One long term storage and one for occasional reads?
Buck for every 4.7Gb is a very cost effective solution to me....

[KuroNeko]

Unfortunately, it's not as simple as that. DVDRs don't have a date until they're guaranteed to be OK. And you can't see it until it's too late. You just notice one day that several files are corrupted, or the disc is suddenly not recognised.

With Flash memory's stability against light and magnetic fields, I hoped it would be more reliable than DVDRs and HDs.

Neko

[Nurhisham Hussein]

Question. What happens to CDs and DVDs if the are kept for further than 5-10 years?


If my flaky memory hasn't completely gone on the fritz, I think it has to do with the oxidization of the material of the recorded layer.

[Cybrid]

If my flaky memory hasn't completely gone on the fritz, I think it has to do with the oxidization of the material of the recorded layer.
Well...I learn't something new...Did a bit of reading between this.

Measures of CD-R Longevity (http://www.mscience.com/longev.html)

Stability Comparison of Recordable Optical Discs (http://www.itl.nist.gov/div895/gipwg/StabilityStudy.pdf)

To overcome the preservation limitations of burnable CDs, Gerecke suggests using magnetic tapes, which, he claims, can have a life span of 30 to 100 years, depending on their quality. "Even if magnetic tapes are also subject to degradation, they're still the superior storage media," he said.
Source (http://computerworld.com/hardwaretopics/storage/story/0,10801,107607,00.html)

Ok. So there is tape.... :lol:

Seriously though. I fail to see how making two copies. One kept climate controlled, one for everyday use (which will undoubtedly wear out faster) could be beat. 5 years later...renew your backup...use quality discs...

Now off I go to weed through years of CD's (Choice language not fit for young years) :roll: