I am considering getting a small ssd for my operating system but i am only running sata 2. I know that a sata 3 will work on sata 2 at a diminished speed and will be faster then any platter HDD out there. If i was to get a drive with 500mb/s read and write would i even be able to tell the diffrence on a sata 2 or 3 connection ? . I know sata 2 is 3gb/s and i know that it will never actualy max out at said speed but surley it is capable for reaching 500mb/s. Or perhaps should i stick with an ssd with half the read write say 250mb/s.
SATA II's throughput is 3 Gbp/s (300MB/s - with overhead) so your average SATA II SSD doesn't quite get there. A SATA III drive will saturate it but still be much faster than a mechanical and somewhat faster than one that is SATA II.
If you can find a good deal go SATA III so you can carry it into a new build at some point, otherwise, get what you can and enjoy either way!