Evaluation of site availability exploitation towards performance optimization in data grids

Data in distributed systems are often replicated into different storage elements in order to facilitate their access. This allows optimizing execution time and bandwidth consumption, ensures load balancing and increases data availability and quality of service. Several replication strategies have then been proposed in the literature. In this work, a new evaluation metric for replication strategies is introduced and experimentally evaluated. This metric, called SAvE, serves to tackle a key feature, although neglected in the literature, which is the ability of a replication strategy to exploit the most available sites in the system. The design of such a metric requires an accurate determination of the availability degree of each site. A new measurement of site availability, denoted SA, is then designed to be integrated into SAvE while overcoming the drawbacks experienced by existing measurements. Extensive experiments are performed using the OptorSim simulator to show the accuracy and the effectiveness of our contributions.