We would like to thank John Schimmel, our shepherd, Douglas Ghormley, Neal Cardwell, Kevin Skadron, Drew Roselli, and Eric Anderson for their advice and comments in improving the presentation of this paper. We would also like to thank Rich Martin, Remzi Arpaci, Amin Vahdat, Brent Chun, Alan Mainwaring, and the other members of the Berkeley NOW group for their suggestions, ideas, and help in putting this work together.