Power and QoS Trade-offs in Web Server Clusters for E-commerce ∗ Relatório Técnico RT-5/06 – Instituto de Computação, Universidade Federal Fluminense

The TPC-W standard for benchmarking web commerce architectures defines a multi-tiered architecture, with a set of web interactions and database transactions, each of them with its respective deadline. The quality of service (QoS) in this context is defined as the fraction of web interactions that the system under test is capable to respond under the specified deadlines. When the system is not at full load, it can scale itself down to an operating point of minimum power consumption, but still with the level of customer sat-isfaction required. Our contributions are theoretical propo-sitions of how to control the QoS in a fine-grained manner so that we can make a close examination of the trade-off be-tween QoS and power consumption. We validate the theoret-ical results showing experiments in a multi-tiered TPC-W e-commerce web cluster implemented in Linux, Apache, PHP, and database postgreSQL. 1