How (NAND) Flash fails (Score 1)

Commercially available memory media is NAND flash which is similar to NOR flash but has roughly a 2 to 1 size advantage. The basic issue with these types of non-volatile memories is that they have a limited number of writes that can take place to any given cell before they become erratic or non-functional. There are two types of NAND flash. SLC memories are good for ~100K cycles, while MLC memories are good for ~10K writes. MLC is what is typically used in commercial products, BTW. To minimize this particular problem, an integrated management controller is used with the physical memory for reasons that I'll explain a little later. This management controller does several very important tasks whenever the memory is accessed. First it performs error checking and control. If the controller detects an error in the data written, it flags the block of memory (in reserved space) so it will not be used in the future and rewrites the data to another block. This rerouting of the data is a second important function and is referred to as bad block management. Finally, the controller also performs a function known as read/write leveling. As you can imagine, if you continually write to the first block of available memory, it would quickly wear out, while the rest of the memory would be in tack. The read/write wear leveling "spreads the love" by writing data to various parts of the physical memory to ensure uniform wear. All this being said, the device, as it ages, would begin to exhibit a decrease in total capacity as the blocks were flagged as bad without a catastrophic failure to the entire device. Several other components may be the culprit for a total failure. If it's a jump drive, there is the USB driver chip and oscillator that could have failed. Jump drives, can even be washed as there is no voltage applied to the individual memory cells to maintain them (hence non-volatile) that would be damaged by short circuiting the PCB from the water. Just make sure that thing is completely dry before plugging it in!