This is the first of a series of posts and links to resources on server storage I/O performance and benchmarking (view more and follow-up posts here).
The best I/O is the I/O that you do not have to do, the second best is the one with the least impact as well as low overhead.
Drew Robb (@robbdrew) has a Data Storage Benchmarking Guide article over at Enterprise Storage Forum that provides a good framework and summary quick guide to server storage I/O benchmarking.