Commissioning and exploitation of the MareNostrum5 cluster at the Barcelona Supercomputing Center for CMS computing

The MareNostrum 5 (MN5) is the newly deployed pre-exascale EuroHPC supercomputer hosted at the Barcelona Supercomputing Center (BSC) in Spain. Its 750,000-core general-purpose CPU cluster offers new opportunities for CMS data processing and simulation but also presents integration challenges within the CMS distributed computing system, particularly due to network segregation for compute nodes. To address these constraints, innovative solutions previously implemented for its predecessor, MN4, have been redeployed, alongside new functionalities to support data-intensive workflows. The system’s expanded shared disk storage and enhanced wide-area network connectivity facilitate efficient staging of input datasets, leveraging MN5’s substantial CPU capacity. This contribution provides an overview of the commissioning efforts and the subsequent exploitation of MN5 for CMS.