ATLAS computing system commissioning: real-time data processing and distribution tests

The ATLAS experiment is commissioning its computing system in preparation for LHC data. Part of this activity consists in testing the data flow from the online data acquisition to the offline processing system, and the distribution of raw and processed data to the external computing centres. A series of functional and rate tests has been performed in 2006 and 2007, allowing the optimisation of the hardware and software components of this system; the last phase of commissioning, the so-called Final Dress Rehearsal, consisting of an integration tests of all components, will take place later in 2007. This paper describes the performed tests, the problems that we encountered, and the solutions we found.