LofoSwitch: An online policy for concerted server and disk power control in content distribution networks

The global content distribution infrastructure is expanding towards the edge of the Internet with cache servers deployed closer to the clients to enable a highly available and bandwidth-efficient delivery of high-quality video services to a broadening range of consumer terminals. The proliferation of cache servers in telco data centers contributes to the unsustainable increase of data-center power consumption. In this paper, we propose to save energy in content distribution networks (CDNs) by means of combined dynamic power management (DPM) of the CDN’s cache servers and the disks in these servers. We present an online load-directed threshold-based power control policy that reduces the CDN’s power consumption while ensuring the best possible viewing experience and a high service availability. In addition, the proposed policy avoids an increase of the bandwidth cost and an excessive wear of the servers and disks. We compare such online policy with a near-optimal offline heuristic greedy policy that determines an upper bound for the energy savings that can be realized by DPM. The evaluation of the power control policies is based on a CDN energy simulator driven by HTTP adaptive-streaming workload traces recorded by an operational telco CDN delivering IPTV services to mobile devices. Even for a minimally provisioned CDN, the online policy reduces the cache-server power consumption by 24%. The energy savings realized by the online policy correspond to 85% of the energy-savings upper bound determined by the offline policy.