Scotgrid: Providing An Effective Distributed Tier-2 In The Lhc Era

ScotGrid is a distributed Tier-2 centre in the UK with sites in Durham, Edinburgh and Glasgow, currently providing more than 4MSI2K and 500TB to the LHC VOs. Scaling up to this level of provision has brought many challenges to the Tier-2 and we show in this paper how we have adopted new methods of organising the centres to meet these. We describe how we have coped with different operational models at the sites, especially concerning those deviations from the usual model in the UK. We show how ScotGrid has successfully provided an infrastructure for ATLAS and LHCb Monte Carlo production, and discuss the improvements for user analysis work that we have investigated. Finally, although these Tier-2 resources are pledged to the whole VO, we have established close links with our local user communities as being the best way to ensure that the Tier-2 functions effectively as a part of the LHC grid computing framework. In general conclusion, we find that effective communication is the most important component of a well-functioning distributed Tier-2.