Clusters of commodity computers are currently being used to provide the scalability required by severalpopular Internet services. In this paper we evaluate an efficient cluster-based WWW server, as a function of the characteristicsof the intra-cluster communication architecture. More specifically, we evaluate the impact of processor overhead, networkbandwidth, remote memory writes, and zero-copy data transfers on the performance of our server. Our experimental results with an 8-node cluster and four real WWW traces show that networkbandwidth affects the performanceof ourserverby only 6%. In contrast, user-level communication can improve performance by as much as 29%. Low processor overhead, remote memory writes, and zero-copyall makesmall contributionstowardsthis overallgain. Tobe able to extrapolatefromourexperimentalresults,we usean analytical model to assess the performance of our server under different workloadcharacteristics,different numbersof cluster nodes, and higher perform...
Enrique V. Carrera, Srinath Rao, Liviu Iftode, Ric