Michael Callahan is an Entrepreneur in Residence at Greylock Partners. Michael was CTO of PolyServe, a Greylock portfolio company that built mission-critical shared-data storage clustering software for Linux and Windows. He cofounded the company in 2000 and helped it grow to deployments at over a thousand customers and a successful acquisition by HP in 2007. He then served as Chief Technologist for Enterprise NAS at HP. Since leaving HP at the end of 2009, he has consulted for various start-ups on development operations and strategy, including Greylock portfolio companies Workday and Drobo (formerly Data Robotics). Before starting PolyServe, Michael served as Director of Advanced Development at Ask Jeeves, an early natural-language search engine. Previously, he was a mathematician, focusing on differential geometry, topology, gauge theory, and the use of scientific visualization in mathematics, and did research in computer science on the application of massively parallel architectures to computer vision. Michael was a Rhodes Scholar and Junior Research Fellow in Mathematics at Oxford University, and graduated from Harvard University summa cum laude with a degree in Social Studies. Yet he still does not reliably remember all the state capitals.