CloudPowerCap: Integrating Power Budget and Resource Management across a Virtualized Server Cluster

摘要

In many datacenters, server racks are highly underutilized. Rack slots areleft empty to keep the sum of the server nameplate maximum power below thepower provisioned to the rack. And the servers that are placed in the rackcannot make full use of available rack power. The root cause of this rackunderutilization is that the server nameplate power is often much higher thancan be reached in practice. To address rack underutilization, server vendorsare shipping support for per-host power caps, which provide a server-enforcedlimit on the amount of power that the server can draw. Using this feature,datacenter operators can set power caps on the hosts in the rack to ensure thatthe sum of those caps does not exceed the rack's provisioned power. While thisapproach improves rack utilization, it burdens the operator with managing therack power budget across the hosts and does not lend itself to flexibleallocation of power to handle workload usage spikes or to respond to changes inthe amount of powered-on server capacity in the rack. In this paper we presentCloudPowerCap, a practical and scalable solution for power budget management ina virtualized environment. CloudPowerCap manages the power budget for a clusterof virtualized servers, dynamically adjusting the per-host power caps for hostsin the cluster. We show how CloudPowerCap can provide better use of power thanper-host static settings, while respecting virtual machine resourceentitlements and constraints.