LHC computing grid ready for restart of the Large Hadron Collider
Wed 8 Jul 2009
The computing grid that will provide the massive amounts of computer power needed to support the experiments at the Large Hadron Collider (LHC ) – the world’s most powerful particle accelerator - has passed a new series of stringent tests that mimicked the immense load it will be under when the LHC restarts later this year.
After months of preparation and two intensive weeks of continual operation, the Worldwide LHC Computing Grid (wLCG) has demonstrated that it is ready to support the massive growth in LHC users once data taking commences.
wLCG combines the IT power of more than 140 computer centres, the result of collaboration between 33 countries. The UK contributes 21 of these sites and almost 15,000 computers. The UK facilities are all managed by GridPP, a project funded by the Science and Technology Facilities Council (STFC).
While there have been several large-scale data-processing tests in recent years, this exercise, called STEP'09, was the first full demonstration involving all of the key elements, from data taking at CERN through to analysis of data at the individual sites worldwide. This stress testing is necessary; once data taking commences, the number of users will grow from several hundred today to several thousand.
During the two weeks the system performed excellently with numerous data processing and data transfer records being established. The ATLAS experiment alone running close to 1 million analysis jobs and achieving 6GB/s of "Grid traffic" sustained over long periods, the equivalent of a DVD worth of data a second. "Unlike previous challenges, which were dedicated testing periods, STEP’09 was a production activity that closely matches the types of workload that we can expect during LHC data taking. It was a demonstration not only of the readiness of experiments, sites and services but also the operations and support procedures and infrastructures", said Ian Bird, leader of the wLCG project.
The results from STEP'09 in the UK have been particularly positive, with the country providing over 2 million hours of computing time. The main computing site in the UK is at the STFC's Rutherford Appleton Laboratory in Oxfordshire and the facilities there performed perfectly providing 10% of the UK's contribution. In other parts of the country Imperial College London, the University of Glasgow and the University of Manchester provided more than 50% of the computing time used in the UK.
David Britton, the GridPP Project Leader reported: "In the UK, STEP'09 ran very smoothly at the majority of sites, which allowed the focus to be on understanding the performance and tuning the infrastructure. The STFC RAL site performed exceedingly well with only a single out-of-hours call out over the two week period. Valuable information was obtained on the performance of tape-drives under realistic workflows; we also added extra data traffic on top of STEP'09 to stress test the networking in and out of the sites in the UK ; and the fairshare system was successfully tuned to balance the load between experiments."
The lessons learned from the particle physics community building the wLCG have allowed researchers from other disciplines to harness the power of grid computing. Enabling Grids for EsciencE (EGEE) is an EC funded project helping support grid users from communities as diverse as computational chemistry and eSocial science. The biomedical community has had particular success investigating avian flu and malaria drugs, running 100 years’ work in 4 months during one phase of their project.
Bob Jones, director of the EGEE project remarked "such a significant achievement is also a valuable testament to the state of maturity of the EGEE infrastructure and its ability to interoperate with major Grid infrastructures in other parts of the world. Ensuring that this level of service continues uninterrupted as we transition from EGEE to its successor European Grid Initiative is clearly essential to our users, including flagship communities such as High Energy Physics."
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