Efficiency and power conservation are critical issues in the design of cluster systemsbecause these two parameters have direct implications on the user experience and theglobal need to conserve power. Widely adopted, distributor-based systems forward clientrequests to a balanced set of waiting servers in complete transparency to the clients. Thepolicy employed in forwarding requests from the front-end distributor to the backendservers plays an important role in the overall system performance. Existing researchseparately addresses server performance and power conservation. The locality-awarerequest distribution (LARD) scheme improves the system response time by having therequests served by web servers which have the data in their cache. The power-awarerequest distribution aims at reducing the power consumption by turning the web serversOFF and ON according to the load.This research tries to achieve power conservation while preserving the performance of thesystem. First, we prove that using both power-aware and locality-aware requestdistribution together provides optimum power conservation, while still maintaining therequired QoS of the system. We apply the usage of pinned memory in the backend servers to boost performance along with a request distributor design based on power and localityconsiderations. Secondly, we employ an intelligent-proactive-distribution policy at thefront-end to improve the distribution scheme and complementary pre-fetching at the backendserver nodes. The proactive distribution depends on both online and offline analysis ofthe website log files, which capture user navigation patterns on the website. The prefetchingscheme pre-fetches the web pages into the memory based on a confidence value ofthe web page predicted by backend using the log file analysis. Designed to work with theprevailing web technologies, such as HTTP 1.1, our scheme provides reduced responsetime to the clients and improved power conservation at the backend server cluster.Simulations carried out with traces derived from the log files of real web servers witnessperformance boost of 15-45% and 10-40% power conservation in comparison to theexisting distribution policies.
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