Yank: enabling green data centers to pull the plug

Abstract

Balancing a data center’s reliability, cost, and carbon emissions is challenging. For instance, data centers designed for high availability require a continuous flow of power to keep servers powered on, and must limit their use of clean, but intermittent, renewable energy sources. In this paper, we present Yank, which uses a transient server abstraction to maintain server availability, while allowing data centers to “pull the plug ” if power becomes unavailable. A transient server’s defining characteristic is that it may terminate anytime after a brief advance warning period. Yank exploits the advance warning—on the order of a few seconds—to provide high availability cheaply and efficiently at large scales by enabling each backup server to maintain “live ” memory and disk snapshots for many transient VMs. We implement Yank inside of Xen. Our experiments show that a backup server can concurrently support up to 15 transient VMs with minimal performance degradation with advance warnings as small as 10 seconds, even when VMs run memory-intensive interactive web applications. 1