After months of preparation and two intensive weeks of continuous operation in June, the LHC experiments celebrated the achievement of a new set of goals aimed at demonstrating full readiness for the data-taking with collisions expected to start later this year. The Scale Testing for the Experiment Programme ’09 (STEP ’09) was designed to stress the Worldwide LHC Computing Grid (WLCG), the global computing Grid that will support the experiments as they exploit the new particle collider. The WLCG combines the computing power of more than 140 computer centres, in a collaboration between 33 countries.
While there have been several large-scale data-processing tests in recent years, this was the first production demonstration to involve all of the key elements from data-taking through to analysis. This allowed different records to be established in data-taking throughput, data import and export rates between the various Grid sites, and in huge numbers of analysis, simulation and reprocessing jobs. The ATLAS experiment ran close to 1 million analysis jobs and achieved 6 GB/s of Grid traffic – the equivalent of a DVD’s worth of data a second, sustained over long periods. This result coincides with the transition of Grids into long-term sustainable e-infrastructures that will be of fundamental importance to projects with the lifetime of the LHC.
With the restart of the LHC only months away, there will be a large increase in the number of Grid users, from several hundred unique users today to several thousand when data-taking and analysis commence. This will happen only through significant streamlining of operations and the simplification of end-users’ interaction with the Grid. STEP ’09 involved massive-scale testing of end-user analysis scenarios, including “community-support” infrastructures, whereby the community is trained and enabled to be largely self-supporting, backed a core of by Grid and application experts.
