  The ScotGrid distributed Tier-2 now provides more that 4MSI2K and 500TB for
LHC computing, which is spread across three sites at Durham, Edinburgh and
Glasgow. Tier-2 sites have a dual role to play in the computing models of the
LHC VOs. Firstly, their CPU resources are used for the generation of Monte
Carlo event data. Secondly, the end user analysis data is distributed across
the grid to the site's storage system and held on disk ready for processing by
physicists' analysis jobs. In this paper we show how we have designed the
ScotGrid storage and data management resources in order to optimise access by
physicists to LHC data. Within ScotGrid, all sites use the gLite DPM storage
manager middleware. Using the EGEE grid to submit real ATLAS analysis code to
process VO data stored on the ScotGrid sites, we present an analysis of the
performance of the architecture at one site, and procedures that may be
undertaken to improve such. The results will be presented from the point of
view of the end user (in terms of number of events processed/second) and from
the point of view of the site, which wishes to minimise load and the impact
that analysis activity has on other users of the system.
