ATLAS Distributed Computing

This paper details the different aspects of ATLAS Distributed Computing experience after the first 1.5 years of LHC data taking. We describe the performance of the ATLAS Distributed Computing system and the lessons learned during the 2010 - 2011 runs, pointing out parts of the system which were in good shape, and also spotting areas which required improvements. We focus on the Site exclusion policy and its implementation, with emphasis on the automatic site exclusion