MultiGreen
Wei Si Deng, Fangming Liu, Hai Jin, Chuan Wu, Xue Liu · 2013
Faced by soaring power cost, large footprint of carbon emission and unpredictable power outage, more and more modern Cloud Service Providers (CSPs) begin to mitigate these challenges by equipping their Datacenter Power Supply System (DPSS) with multiple sources: (1) smart grid with timevarying electricity prices, (2) uninterrupted power supply (UPS) of finite capacity, and (3) intermittent green or renewable energy. It remains a significant challenge how to operate among multiple power supply sources in a complementary manner, to deliver reliable energy to datacenter users over time, while minimizing a CSP's operational cost over the long run. This paper proposes an efficient, online control algorithm for DPSS, called MultiGreen. MultiGreen is based on an innovative two-timescale Lyapunov optimization technique. Without requiring a priori knowledge of system statistics, MultiGreen allows CSPs to make online decisions on purchasing grid energy at two time scales (in the long-term market and in the real-time market), leveraging renewable energy, and opportunistically charging and discharging UPS, in order to fully leverage the available green energy and low electricity prices at times for minimum operational cost. Our detailed analysis and trace-driven simulations based on one-month real-world data have demonstrated the optimality (in terms of the tradeoff between minimization of DPSS operational cost and satisfaction of datacenter availability) and stability (performance guarantee in cases of fluctuating energy demand and supply) of MultiGreen.