[DSMan195276]

> Why don't operating systems treat SSDs as flash memory, and why doesn't the file system cooperate with the underlying hardware instead of pretending it's a disk? For home use that may even work, but in a demanding environment the extra complexity will invariably fail.

The simple reason is because the SSDs themselves expose a regular HD interface and then does a lot of the flash-memory related stuff itself. For example, if you don't include TRIM support (Which early SSDs did not have) there is no 'erase' command the OS can send to an SSD.

With that in mind, SSDs also have memory controllers on them that map the blocks the OS sees to actual SSD blocks (scattered across the memory chips). So when the OS writes to block 1 it may write to block 15 internally on the SSD, and then block 2 might write to block 4002. Combine this with caching and other various details on the SSD side, and it leaves little predictable behavior for the OS to exploit.