ALICE Grid Computing at the GridKa Tier-1 Center

Abstract

Abstract. The GridKa center at the Karlsruhe Institute of Technology is the largest ALICE Tier-1 center. It hosts 40,000 HEPSEPC'06, approximately 2.75 PB of disk space, and 5.25 PB of tape space for the 'A Large Ion Collider Experiment' (ALICE), at the CERN Large Hadron Collider (LHC). These resources are accessed via the AliEn (ALICE Environment) middleware. The storage is divided into two instances, both using the storage middleware xrootd. We will focus on the set-up of these resources and on the topic of monitoring. The latter serves a vast number of purposes, ranging from efficiency statistics for process and procedure optimization to alerts for on-call duty engineers. C Jung . ALICE Grid ComputingThe ALICE experiment is one of the four detectors at CERN LHC. It has been designed to study the physics of strongly interacting matter at extreme energy densities. The ALICE experiment will primarily focus on heavy-ion collisions (in particular Pb-Pb), but also has a physics program for proton-proton and proton-ion collisions.The overall data volume per year is estimated to be about 5 PB without replicas. Half of this is RAW data, the other half consists of first and second level RAW reconstruction, simulated data and user generated data. RAW data and user files have two replicas, first and second level RAW reconstruction data have three replicas.Within ALICE, the Tier-1 centers store parts of the RAW data as well as parts of the first and second level RAW reconstruction data. Typically, the computing jobs running at Tier-1 centers are second pass reconstruction, Monte Carlo simulations, and user analysis. Currently, there are six ALICE Tier-1 centers worldwide [1].