There is an interesting term that I came across, called IOPS. IOPS stands for Input / Output operations per secon.

IOPS can be measured with an IOmeter, the IOPS matrix is particularly used as a performance matrix for measuring the read and write operations in hard drives and solid state drives, and in some cases Storage Area Networks (SAN).

A 7200 RPM drive typically will perfom on approximately 75 to 100 IOPS fro a typical SATA 3 Gb/s hard drive. This as compared to 60,000 IOPS on a OCZ brand name solid state drive for the same SATA 3 interface.

If you are interested in further details about this spec, the complete details are available at its WIKI at http://en.wikipedia.org/wiki/IOPS