Dynamic data replication in LCG 2008

To provide performant access to data from high energy physics experiments such as the Large Hadron Collider (LHC), controlled replication of files among grid sites is required. Dynamic replication in response to jobs may also be useful, and has been investigated using the grid simulator OptorSim. In this paper, results from simulation of the LHC Computing Grid in 2008, in a physics analysis scenario, are presented. These show, first, that dynamic replication does give improve job throughput by optimising resource usage; second, that for this complex grid system, simple replication strategies such as LRU and LFU are as effective as more advanced economic models; third, that grid site policies which allow maximum resource sharing are more effective; and lastly, that dynamic replication is particularly effective when data access patterns include some files being accessed more often than others, such as with a Zipf-like distribution.