How to Achieve High Throughput with Dynamic Tree-Structured Coterie

Data replication permits a better network bandwidth utilization and minimizes the effect of latency in large-scale systems such as computing grids. However, the cost of maintaining the data consistent between replicas may become difficult if the read/write system has to ensure sequential consistency. In this paper, we limit the overhead due to the data consistency protocols by introducing a new dynamic quorum protocol called the elementary permutation protocol. This protocol permits the dynamic reconfiguration of a tree-structured coterie (Agrawal and Abbadi, 1991) in function of the load of the machines that possess the data replicas. It applies a tree transformation in order to obtain a new less loaded coterie. This permutation is based on the load information of a small group of machines possessing the copies. The implementation and the evaluation of our algorithm have been based on the existing atomic read/write service of Lynch and Shvartsman (1997). We demonstrate that the elementary permutation ameliorates the system´s throughput up to 50% in the best case. The results of our simulation show that the tree reconfiguration based on the elementary permutation is more efficient for a relatively small number of copies