SD card shelf-life
 

Hi all,
In a related thread, I asked if it was safe to continue using a 10 year old SD card in an embedded application even if it was in read-only mode the whole time. The consensus seemed to be that it should be replaced without further delay. Now, I have replaced the card in question with a brand new one and dd'd the data from the old card onto it and am feeling smugly secure now for the next 10 years as a result. However, it does kind of beg the question: does the 'data integrity clock' start running from the time the card is manufactured or from the time it's last written to? In other words, rather than replacing the old card, could I have got away with just over-writing it freshly with the same data as originally on it? Would that have got me another 10 years with it?
cheers,
Jinxie

The thing I have heard most about is the low write cycles on sd cards.If you held an sdcard for 10 years and it still worked, I might approach the Guinness Book of records with the oldest sd card in service :D.

OTOH, if you wanted this data to be written continuously for ten years, and chose to store it for that time on an sdcard, we wouldn't think you're clever. But we know little of the application. If the data was cached, it might not have been exercised. Posters here can't give negative reputation, but perhaps the moderators would make an exception :D.

SD cards should last a reasonable time in read only mode, but won't last too long if being constantly written to.

(It's the same with pendrives.)

Regular disk drives are built for lots of read/write cycles, so last longer - but then, how long is a piece of string.... ;)

If it is important, spend the money, & change it fairly regularly - only you know how important it is. :)

They publish MTBF for them and they seem to fail way before that guess.

I'd have a clone of the drive and a good backup. Any flash media is subject to total failure.

Well, I just wonder how many savers and investors have huge amounts of money in the form of Bitcoin stashed away on such flash drives, on the unquestioning assumption that they'll be good for ever? Most such people would be my guess - and most of those again blissfully unaware of the dangers of stray magnetic fields. The ever-increasing prevalence of powerful neodymium-boron magnets in many common, day-to-day objects magnifying that danger again by an order of magnitude!

The newest ones made with the newer technology have the potential to last a LOT longer. But all storage fails, just make sure you have a backup.

I think Bitcoin is a Ponzi scheme so I don't care if they go south.

I'm waiting on ultra computers so I can print my money and drive down their coins.

These e-coins are not serious investments and anyone who believes they are must be delusional. They should be regarded in the same light as playing slots at a casino IMV. You can have a bit of fun if you can afford to lose it all - which you will if you stay in the game long enough.
So good luck with your ultra computer and I'll be laughing along with you if you pull it off!

A flash drive that is not powered will slowly lose its charge but data retention is maybe 10 years. I have a few that are at least 10 years old that I check every once in a while and have not lost anything and (There is nothing worth saving on them regardless) plugging them in does reset their charge. There is also something called read disturbance where a large number of reads could corrupt nearby cells causing errors.

In your case the memory is constantly powered, once booted the system probably does not access the drive much so there should not be any read disturbance. IMHO it is better to be safe then sorry and replace the drive as a precautionary measure.

Somewhere I still have some sdcards that are probably 15+ years old, maybe older (8-128MB). If I find them, I'll see if the data on them is still readable.

Are you sure it resets the charge? Being a hardware head, I'm trying to imagine the mechanism whereby 'resetting the charge' actually happens. Of course my education contained nearly as much about thermionic valves ('tubes' to folks in the Excited States) as semiconductors. Wafer fab was then measured in micrometres.

EDIT: I can't imagine myself wanting much that's 10 years old. And if I did, an sdcard is the LAST place I'd leave it.

Maybe not. I suppose then the only way would be to copy the data and then rewrite it back.

That would be the better approach.
The media is different, as is the mechanism, but the user principal is the same. I have floppy disks from the 1970s that I cannot rewrite because they were written in quad density on CP/M machines that I no longer have. I have floppy disks from the late 1980s that I can refresh, if I can just resurrect one of my DOS machines and the floppy drive still works. After all this time the information on those floppies is getting weak and difficult to read. Normal magnetic flux from the earth's fields, 120MHz hum from the power lines in the walls, and just normal aging has slowly erased the media. If you have media with data of value you back it up, but also read and rewrite the data on some schedule to prevent degradation and normal aging from destroying your data in place. If you have tapes, you at least run and rewind them occasionally to prevent the tape from sticking or getting so brittle it becomes worthless.
Consider it part of your normal maintenance routine.

My philosophy on data is simple. Always keep the data you want 'spinning'. Period. Obviously keep backups and off-site backups of that data. Since one frequently backups up data (or should), the backup media will always be on media that you can restore from if necessary and the 'spinning' data will be on the latest media type (in my case SSDs). Never just backup data and then delete your spinning data to save space or something. Disk space is cheap. Use it. You'll always be able to go back to old data if needed. When you pass (happens to all of us), your kids can save/delete whatever they want, but you'll be past caring at that point.

SD cards are cheap, but buy good ones. I've started to buy the 'durable' ones (more expensive) even though a bit slower. Most SD card situations, speed isn't why you use them.