Improvements in utilisation of the Czech national HPC center by ATLAS distributed computing

The ATLAS distributed computing is allowed to opportunistically use resources of the Czech national HPC center IT4Innovations in Ostrava. The jobs are submitted via an ARC Compute Element (ARC-CE) installed at the grid site in Prague. Scripts and input files are shared between the ARC-CE and shared file system located at the HPC via sshfs. This basic submission system has worked there since the end of 2017. Several improvements were made to increase amount of resource that ATLAS can use. The most significant one was the migration of the submission system to enable pre-emptable jobs, as the HPC management made the decision to use pre-emption on opportunistic jobs. Another improvement of the submission system is related to the sshfs connection which seemed to be a limiting factor of the system. Now, the submission system consists of several ARC-CE machines. Also, various parameters of sshfs were tested in an attempt to increase throughput. As a result of the improvements, the utilisation of the Czech national HPC center by the ATLAS distributed computing increased.