Abstract
Data Grids provide geographically distributed storage for large-scale data-intensive applications. Ensuring efficient access to such large and widely distributed datasets is hindered by high latencies. To speed up data access, Data Grid systems replicate data in multiple locations so a user can access the data from a nearby site. In addition to reducing data access time, replication also aims to use network and storage resources efficiently. While replication is a well-known technique, the problern of replica placement has not been, widely studied for Data Grid environments. To obtain the best possible gains from replication, strategic placement of the replicas is critical. In a grid environment, resource availability, network latency, and users' requests can vary. To address these issues, a placement strategy is needed that adapts to dynamic behavior. This paper proposes a new dynamic replica placement algorithm for hierarchical Data Grids based on file "popularity". Our goal is to place replicas close to the clients to reduce access time while using the network and storage efficiently thereby effectively balancing storage cost and access latency. We evaluate our-algorithm using OptorSim [1] which shows that our approach outperforms other techniques in terms of access time and bandwidth used.