What about SLC SSDs? I heard that SLC is better than MLC, regarding max writes.
A good point, however like DRAM most of the manufacturers are pushing the process and thus quality as hard as possible. This is because the price per megabit of flash has plummeted. Just like DRAM did. That being said the MLC parts are popular because they store more and are cheaper. They just don't wear as well because cells store a multi level charge which has issues with maintaining an exact voltage to get back. There has been a huge rush in the last few years to REPLACE flash. So it's getting closer to the end of flash than most people realize. If you are curious look at the
Wikipedia article.
Capacity is obviously different between
MLC and SLC (Wikipedia again).
The SLC versus MLC
does drastically affect endurance. The solution has been to use built in controllers for handling the FEC (instead of a processor).
Forward Error Correction is ... quite complex and has a large amount of software work required, the compact disk format uses Reed-Solomon encoding to fix long bit errors. This is fairly similar to what they have to use with NAND devices to improve 'endurance' but in reality is actually just improving FAULT tolerance (IE it's failure edge is slightly blurred by using extra data to correct for defective bit errors).
Samsung parts are fairly decent and most of theirs are at the 100k mark. They do have bad memory blocks however. All of manufacturers do.
Sandisk is Toshiba, I don't know who they sold there NAND flash operations too but they still appear to be making SD cards (re-branded possibly?)
For SSD drives most of the 'real' part of the system is in the controller and how they handle these bit errors. Unfortunately compared to a hard disk the number of errors is much greater in flash. It's main bonus is speed (Flash that is) because it has no mechanical latency issues (just write and read speed bottle necks).
The second issue for SSD is power a lot of the manufacturers go on how much lower power it is etc. However any read or write uses power just like on a hard disk. They use lots of caching schemes to manage power in an SSD system. As you must be careful how much power you draw especially in a laptop. Again SOFTWARE mostly handles this as well.
How long what is in the memory lasts is a bit more complex. Each of the memory cells are essentially buckets of charge. Over time those loose charge via leakage (heat) or read disturbances etc. Some memories are good for 100 years some much less. At least they aren't as bad as say "FLOPPY" disks. Those things just go bad looking at them (well actually the media they are made of corrodes). Certain CD materials do the same thing apparently as well. >SIGH<
Cyb
