ATLAS job submission system for Salomon HPC based on ARC-CE

The ATLAS experiment at CERN is using HPCs opportunistically to extend its computing capacity for years. To the Salomon HPC, ATLAS jobs come via ARC-CE machines located in the computing center of the Institute of Physics of the Czech Academy of Sciences. The ARC-CE serves as an interface between job management systems of the ATLAS and the HPC. Commands of the PBSpro batch system are submitted via ssh. Scripts and input files are shared between the ARC-CE and shared file system located at the HPC via sshfs. There are several aspects of interaction between ARC-CE machines and Salomon's batch system which are important for performance of the whole system. First, the allowed amount of requests to PBSpro is limited and the ARC-CE needed to be adapted to this fact. Second, the sshfs connection speed seems to be a limiting factor for job turnaround. Some possibilities of sshfs parameters tuning were investigated. Moreover, monitoring allows quick detection of issues and therefore helps the performance of the system. The ARC-CE based job submission system has adapted to conditions of the Salomon HPC and utilizes successfully its resources.