I’ve searched around for a while out of curiosity, but i can’t find any good numbers on how long flash memory can supposedly last. Figures for MTBF are anywhere between 500k and several million cycles, but if i just stuck a thumb drive in my drawer, how long would it last before the data was corrupted/unrecoverable? Years? Decades? More?
It depends on how many times you’ve cycled the memory - each write / erase cycle reduces the longevity of the data. Most memories are rated for something like 10 years of data retention even after 1,000,000 cycles.
I was just theorizing write once, and let it sit, i.e. archival use, so a very low amount of cycles.
10 years isn’t so hot.
Ive seen cheap USB thumb drives fail from just sitting around too long. I would not consider flash media as we know it to be archival quality. Perhaps that will change when SSD comes around, but generally we can only speculate. Whatever you do make sure you have this data stored elsewhere on a different medium.
Freescale says it’s better than 100 years. (PDF)
According to wikipedia silicon has a half-life of 170 years. So that must be the absolute maximum. After 170 years it wouldnt be silicon, and not capable of storing memory. Jusr a WAG
The only silicon with a half-life is synthetic according to your site. Natural silicon isn’t radioactive.
My sand!
What happened to all my sand!
It was right there!
That’s very interesting. This isn’t a question that’s often addressed (or asked). Too bad they don’t go into details of the actual error rates, the ECC compensation of thumb drive controllers, the contribution of radiation and cosmic rays over such a long period of time, or the failure rates of the other components of a thumb drive. But, things are looking good.
I’ve been eyeing the netbook computers, and some of them have flash based hard drives ~16gb. Those hard drives might see a good bit of use, or at least some parts of them might. I’m wondering how long they’re expected to last, but haven’t found any good data on that either.
I’m guessing most flash memory devices will be obsolete long before they are worn out…TRM
I work on embedded devices that use flash memory. We typically budget a total of 100,000 write cycles to a particular location before the flash there is degraded. To extend the life, most flash drivers cycle thru the physical addresses on the part as data is added to avoid writing to the same location over and over.
How long the physical device will last will depend on the quality of manufacture and how you treat it. If you stick it in a drawer, it’ll probably last a long time. If you set it on the dashboard of your car in 105 degree weather for months on end, probably it won’t last too long.
How long it will last in terms of rewrites, that’s again going to vary quite a bit. A lot of CF cards simply used FAT32 as their file system, I think, which meant that if a single sector died, that could have killed your whole drive depending on where it was. Modern flash drives probably use a file system built for flash that rotates through to spread reuse around, and shrinks the available memory space as sectors die. Modern flash drives might also have spare memory that gets swapped in transparently as sectors die.
For something acting as an internal hard drive, figure that the people making the device wouldn’t have installed it if it wouldn’t last long enough for most users purposes and the overall expected lifespan of the device itself. That will probably be anywhere from 5-10 years. For thumb drives, though, who knows. Unless you’re hearing about people’s thumb drives going dead left and right, I doubt you need to worry about it terribly, but ultimately you shouldn’t consider it as being any better a storage device than an old 5 1/2" floppy disk. Use it to move something from point A to point B, and then consider the contents on it to be trash.
The term is Wear Levelling, and most flash file systems will employ some form of this to ensure that all the areas of the flash card are being used evenly - so even if you repeatedly write to the same address, unknown to you the flash device is actually directing that data to the least-used sections of the card.
If you’re writing reasonably sized amounts of sequential data reasonably infrequently (e.g for archival or in a camera or MP3 player) then this should be all that’s needed to ensure that you get the maximum life from your device. If you take reasonable care of it (and buy from a known manufacturer with a decent reputation) then there’s no reason to expect that the data on it shouldn’t be safe for years.
Operating systems however are another kettle of fish entirely and write their data in a completely different way. Traditional flash file systems are poorly equipped to deal with this and this is why trying to create an SSD on the cheap by running an OS from a USB stick or CF/SD card is a surefire way to kill the device.
The SSD drives in netbooks and laptops will have file systems which are specifically designed for OSes to be run from them.
In what universe did they make 5 1/2" floppy disks?
Hm… Well close enough for government work.