Effective Dynamic Replica Maintenance Algorithm for the Grid Environment

Replication in Data Grid reduces access latency and bandwidth consumption by creating multiple data copies. One of the challenges in data replication is to select the candidate sites where replicas should be placed, which is known as the allocation problem. One performance metric to determine the best place to host replicas is select for optimum average response time. We use the p-median model for the replica placement problem. The p-median model has been exploited in urban planning to find locations where new facilities should be built. In our problem, the p-median model finds the locations of p candidate sites to place a replica that optimize the aggregated response time. Motivated by the fact that the Grid environment is highly dynamic, we propose a dynamic replica maintenance algorithm that re-allocates replicas to new candidate sites when a performance metric degrades significantly. Simulation results demonstrate that the dynamic maintenance algorithm with static placement decisions performs best in dynamic environments like Data Grids.