A data caching model for Tier 2 WLCG computing centres using XCache

Abstract

As the WLCG continues to consolidate the data storage resources to reduce maintaining costs, more storage elements will be decommissioned or federated in the future. In both cases data streaming would become a common method for data accessing in many LHC Tier 2 and Tier 3 computing centres which makes it vital to optimise the network usage (i.e. latency reduction and bandwidth utilisation). Consequently, the data cache service sits closely to the computing resources becomes a desirable tool. In this paper we discuss how to setup a XCache server at an example WLCG Tier 2 site (Edinburgh) and use the ATLAS analysis queue as a testbed to study the data caching performance. The results could be used to guide the future development to make the caching server more effective.