KnightShift: Shifting the I/O Burden in Datacenters to Management Processor for Energy Efficiency

Abstract

Data center energy costs are growing concern. Many datacenters use direct-attached-storage architecture where data is distributed across disks attached to several servers. In this organization even if a server is not utilized it can not be turned off since each server carries a fraction of the permanent state needed to complete a request. Operating servers at low utilization is very inefficient due to the lack of energy proportionality. In this research we propose to use out-of-band management processor, typically used for remotely managing a server, to satisfy I/O requests from a remote server. By handling requests with limited processing needs, the management processor takes the load off the primary server thereby allowing the primary server to sleep when not actively being used; we call this approach KnightShift. We describe how existing management processors can be modified to handle KnightShift responsibility. We use several production datacenter traces to evaluate the energy impact of KnightShift and show that energy consumption can be reduced by 2.6X by allowing management processors to handle only those requests that demand less than 5% of the primary CPU utilization.