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Having trouble installing a piece of hardware? Want to know if that peripheral is compatible with Linux?
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I'm not so sure about that. It's more probable that you trash the stick yourself or lose it, than use it till it's dead I've bought a memory card for my camera, which is more or less the same as other flash drives, and they gave me a 10-year guarantee. The camera writes rather big files (in raw format several dozen megabytes easily) and it's not a shot or two a day, it could easily be hundred of shots a day or even more (you know, one can take about 10 pictures every second with an appropriate shoot mode, so...). If that use lasts for more than 10 years, I doubt if flash memory keys etc. break up just because of daily usage too soon.
Considering the price of those devices, usually 10-20$ for a gigabyte stick or less, I wouldn't be scared. If you are afraid you lose data, you could buy a new stick every year and copy the contents with dd or something. And still I doubt if the old stick would die for it's old age; I see flash memory sticks break up more often because of a manufacturing flaw or a lightning strike than because they've reached their "end of life".
There is no definite finite amount of writes a flash chip can withstand. They have a specified number of writes that they can reliably withstand, after that, you increase the probability of a memory location failing. A flash drive can take about 1,000,000 writes before it starts losing reliability. After that, memory locations may/will begin failing.
Note that since block devices are written to in a least sector-sized blocks (512 bytes), if any location fails, then the whole sector must be discarded (marked as a bad block). In this respect, it's no different to a hard drive. Of course, just beause a few location fails, doesn't mean the whole drive will no longer work, especially if some sectors are written to much more than others.
Note that with a 1,000,000 write lifespan, a device will last for about 10,000 days (27 years) with 100 writes a day, so a long as you don't mount a flash drive on /tmp for example, there shouldn't be too much to worry about.
Be aware though, that most unix filesystems write the atime (access time) every time a file is accessed (avoid this with the noatime option in /etc/fstab). Obviously, in the extreme case, this can knacker a flash drive in a few months if you're accessing it a lot. Thus, it's a good idea to use a filing system (e.g. jffs2) that is specifically designed for flash devices. These filesystems distribute writes across the device, so that no particular sector receives a high number of writes compared to the others.
Each memory cell (storing one bit) has a limited amount of writes. The problem will occur in cells that are written often. As most users use it formatted with FAT, the fat will be the weak point. At the moment that the fat can no longer be updated correctly, you have a problem.
Starting a program is a read-only operation; however the program might write data at startup to the stick.
A memory stick is not a backup device ! It's not reliable enough.