Improving Data Grids Performance by using Modified Dynamic Hierarchical Replication Strategy

A data grid connects a collection of geographically distributed computationaland storage resources that enables users to share data and other resources. data replication,a technique much discussed by data grid researchers in recent years creates multiple copiesof file and places them in various locations to shorten file access times. in this paper, adynamic data replication strategy, called modified dynamic hierarchical replication(mdhr) is proposed. this strategy is an enhanced version of dynamic hierarchicalreplication (dhr). however, replication should be used wisely because the storagecapacity of each grid site is limited. thus, it is important to design an effective strategy forthe replication replacement task. mdhr replaces replicas based on the last time the replicawas requested, number of access, and size of replica. it selects the best replica locationfrom among the many replicas based on response time that can be determined byconsidering the data transfer time, the storage access latency, the replica requests thatwaiting in the storage queue, the distance between nodes and cpu process capability.simulation results utilizing the optorsim show mdhr achieves better performance overallthan other strategies in terms of job execution time, effective network usage and storageusage.