Efficiency vs. portability in cluster-based network servers

Efficiency and portability are conflicting objectives for cluster-based network servers that distribute the clients' requests across the cluster based on the actual content requested. Our work is based on the observation that this efficiency vs. portability tradeoff has not been fully evaluated in the literature. To fill this gap, in this paper we use modeling and experimentation to study this tradeoff in the context of an interesting class of content-based network servers, the locality-conscious servers, under different inter-node communication subsystems. Based on our results, our main conclusion is that portability should be promoted in cluster-based network servers with low processor overhead, given its relatively low cost ($\leq$ 16%) in terms of throughput performance. For clusters with high processor overhead communication, efficiency should be the overriding concern, as the cost of portability can be very high (as high as 107% on 96 nodes). We also conclude that user-level communication can be useful even for non-scientific applications such as network servers.