Saving 200kW and $200 K/year by power-aware job/machine scheduling

This paper reports our 3.75-year empirical study on power-aware operations of Kyoto University´s supercomputer system. The supercomputer system of 10 TFlops had required about 540 kW on average in its first fiscal year 2004. After that and one-year try-and-error of power efficient operation, we implemented a simple but effective scheduler of jobs and machine powering to improve the per- load power efficiency by up to 39 % and to save 200 kW and $200,000 electric charge in the fiscal year 2006. The power-aware scheduler tries to minimize the number of active nodes in the system of eleven nodes keeping sufficient computational power for given loads. Thus the power- aware scheduler has not degraded, but has significantly improved, the service quality in terms of the average job- waiting time.