Dynamic Voltage Scaling in Multi-tier Web Servers with End-to-End Delay Control

Energy and cooling costs of web server farms are among their main financial expenditures. This pa- per explores the benefits of dynamic voltage scal- ing (DVS) for power management in server farms. Unlike previous work, which addressed DVS on in- dividual servers and on load-balanced server repli- cas, this paper addresses DVS in multi-stage service pipelines. Contemporary Web server installations typically adopt a three-tier architecture in which the first tier presents a Web interface, the second exe- cutes scripts that implement business logic, and the third serves database accesses. From a user�s per- spective, only the end-to-end response across the en- tire pipeline is relevant. This paper presents an al- gorithm for minimizing the total energy expenditure of the multi-stage pipeline subject to soft end-to-end response-time constraints. A distributed power man- agement service is designed and evaluated on a real 3-tier server prototype for coordinating DVS settings in a way that minimizes global energy consumption while meeting end-to-end delay constraints. The ser- vice is shown to consume as much as 30% less energy compared to the default (Linux) energy saving policy.

Horvath, Tibor, Tarek Abdelzaher, and Kevin Skadron. "Dynamic Voltage Scaling in Multi-tier Web Servers with End-to-End Delay Control." University of Virginia Dept. of Computer Science Tech Report (2004).