The importance of switch dimension for energy-efficient datacenter design

摘要

Saving power in datacenter networks has become a pressing issue as the networks tend to consume steady power even when many servers may be idle during periods of low activity. While in operation, ElasticTree and CARPO can save power consumed by a fat-tree network by using sleep mode, where some components such as ports and switches are turned off when traffic demand in the network is relatively moderate. In this paper, we propose a new approach by exploring the design stage of a datacenter network, and focus on how to choose the right switch size that can potentially save the most power during the expected operation of the network. We also consider speed scaling where the power of a switch can be varied by adjusting its processing rate according to its traffic demand. We first perform analysis and simulation to investigate the power-saving performance of different switch sizes, power-saving modes and traffic demand patterns. Based on fat-tree networks with sleep mode and supporting a fixed number of servers, our findings reveal that deploying a large number of small switches is more power-efficient than a small number of large switches when the traffic demand is relatively moderate or when servers exchanging traffic are in close proximity. With speed scaling, the reverse is generally true. We confirm our findings using traffic traces from a production datacenter. Our approach for studying the fat-tree topology design is also extendible to other types of datacenter network topologies.