ATLAS off-Grid sites (Tier-3) monitoring. From local fabric monitoring to global overview of the VO computing activities

ATLAS is an LHC (Large Hadron Collider) experiment at the CERN particle physics laboratory in Geneva, Switzerland. The ATLAS Computing model embraces the Grid paradigm and originally included three levels of computing centers, in order to handle data volumes of multiple petabytes per year. With the formation of small computing centers, usually based at universities, the model was expanded to include them as Tier-3 sites. Tier-3 centers comprise a range of architectures and many do not possess Grid middleware, thus, monitoring of storage usage and analysis software is not possible for the typical Tier-3 site system administrator, similarly, Tier-3 site activity is not available for the virtual organization of the experiment. In this paper an ATLAS off-Grid site-monitoring software suite is presented. The software suite enables monitoring of sites not covered by the ATLAS Distributed Computing software.