raymor

It's a lot faster for many small files, what geeks call random IO. Booting the OS uses a lot of small files, for example, so an SSD will boot a lot faster. It's not better for big sequential files, like video.

The difference is, with a spinning drive, the system has to read one file, then wait for the drive spin around to where the next file is. It also has to move the mechanical read/write head to the right track. With flash, both thumb drives and USB, there are no moving parts, so no waiting to get to the next file.

Big files like videos are stored sequentially, so there's no jumping around and therefore no advantage for flash (SSD).

How much of an improvement depends also on how much RAM you have. It's small files that SSDs do faster, but it's also small files that get cached in RAM anyway and reordered for writing, so with gobs of RAM the disk doesn't get as much random IO. An example is one of our Clonebox servers, which has 32 GB of system RAM. The RAID cards have another 1 GB of cache, and there's 512 MB of cache on the drives themselves. That means there is plenty of RAM to save up those small writes and write them out in sequential order, so SSDs wouldn't help us much.