Grid-based Simulation Computing in ALICE

The ALICE Collaboration is an active member of the EDG (also known as DataGrid) project since the very beginning; it took active part in the definition of user requirements and detailed use cases, as well as in the evaluation of the EDG testbed, all along its evolution. In December 2001, ALICE ran the first application job on the testbed, the simulation of a low multiplicity Pb-Pb event at the LHC energy. In parallel, because of the deadlines set by its scientific program, ALICE developed the AliEn environment, on which simulated data are regularly produced, reconstructed and analysed on a distributed system scattered over four continents. AliEn has been interfaced with EDG, in order to allow the coordinated management of both ALICE-owned and EDG resources: recently, the simulation of a central Pb-Pb event, submitted as an AliEn job with the requirement to run on EDG resources, was successfully completed, with output registration in the Data Management System on both sides and retrieval of the output, stored on EDG, from the AliEn shell. Meanwhile, making use of an ALICE developed WEB interface, a continuous monitoring of the EDG testbed, with an increasing job and data rate, is in place to evaluate the system stability and to define its breaking point. After two years of work several goals have been achieved, while some items still need improvements in order to run large productions and analysis on a stable, distributed, scalable and interoperable system.