[dragontamer]

SSDs are still grossly slower than RAM. The fastest SSD I know of is the Intel 750, which is like ~2.0 GigaBYTES/second (or for what is more typical for storage benchmarks: about 16Gbps or so over PCIe x4).

Main DDR3 RAM is something like 32GigaBYTES per second, and L1 cache is even further.

What I think the poster was talking about, is moving from disk-based databases to SSD-based databases. SSDs are much faster than hard drives.

L1 Cache, L2 Cache, L3 Cache, and main memory are all orders of magnitude faster than even the fastest SSDs today. Thinking about the "CPU prefetcher" when we're talking about SSDs or Hard Drives is almost irrelevant due to the magnitudes of speed difference.