Using batteries to reduce the power costs of Internet-scale distributed networks

Modern Internet-scale distributed networks have hundreds of thousands of servers deployed in hundreds of locations and networks around the world. Canonical examples of such networks are content delivery networks (called CDNs) that we study in this paper. The operating expenses of large distributed networks are increasingly driven by the cost of supplying power to their servers. Typically, CDNs procure power through long-term contracts from co-location providers and pay on the basis of the power (KWs) provisioned for them, rather than on the basis of the energy (KWHs) actually consumed. We propose the use of batteries to reduce both the required power supply and the incurred power cost of a CDN. We provide a theoretical model and an algorithmic framework for provisioning batteries to minimize the total power supply and the total power costs of a CDN. We evaluate our battery provisioning algorithms using extensive load traces derived from Akamai's CDN to empirically study the achievable benefits. We show that batteries can provide up to 14% power savings, that would increase to 22% for more power-proportional next-generation servers, and would increase even more to 35.3% for perfectly powerproportional servers. Likewise, the cost savings, inclusive of the additional battery costs, range from 13.26% to 33.8% as servers become more power-proportional. Further, much of these savings can be achieved with a small cycle rate of one full discharge/charge cycle every three days that is conducive to satisfactory battery lifetimes. In summary, we show that a CDN can utilize batteries to significantly reduce both the total supplied power and the total power costs, thereby establishing batteries as a key element in future distributed network architecture. While we use the canonical example of a CDN, our results also apply to other similar Internetscale distributed networks.