Project leader: Tomas Lindén   Personnel

HIP supports the computing needs of the LHC experiments ALICE and CMS. ALICE computing resources in Finland are part of the distributed Nordic Data Grid Facility (NDGF) Tier-1 resource within the Nordic e-Infrastructure Collaboration (NeIC), while the CMS resources are of Tier-2 level using some services from NDGF. These Tier-1 and Tier-2 resources are part of the distributed Worldwide LHC Computing Grid, WLCG. The good performance of WLCG is an essential factor in all the physics analyses and publications.

The HIP computing activities are currently focused on analysing the CMS data from Run 2 and 3 using the Finnish Tier-2 centre grid and cloud resources. The project team consists of T. Lindén (project leader) M. Myllymäki and S. Lehti. HIP is represented in the Nordic LHC Computing Grid (NLCG) Steering Committee by T. Lindén.

Data intensive GRID computing

Currently the computing activities consist of analysing the accumulated Run 2 and 3 data and to produce corresponding Monte Carlo data. This needs adequate high performing computing resources and storage at the participating universities and institutes to cope with the data analysis requirements.

The ALICE and CMS computing resources are managed in collaboration with the Finnish IT Center for Science (CSC). ALICE data management is integrated with the NDGF distributed dCache Storage Element for disk. The Finnish ALICE dCache storage capacity is 2100 TB. Job submission is handled through a single server, an ALICE VOBOX that interfaces the local batch system with the ALICE grid middleware ALIEN. The ALICE CPU resources consists of a virtual cluster called alice-tron run on the CSC cPouta cloud system. The renewal of the CSC national supercomputing environment in 2026 gives a possibility to increase the ALICE CPU resources according to the requirements. The CSC HPC cluster Roihu to be available in 2026 is also a possibility for CMS to make use of larger amounts of CPU. Work is ongoing to adapt HEP workloads around constraints of the CSC HPCs Lumi, Mahti and Puhti.

The most important CMS Tier-2 services are end user data analysis on the grid and Monte Carlo simulation production, which need to run uninterrupted while migrating to new hardware, software and/or new services. CMS uses an approach where a set of services needs to be provided for a working Tier-2 site are distributed over the available resources. These services run partly in Kumpula and Viikki and partly at CSC in Kajaani. There is for reliability two Squid proxies running the CMS Frontier service in Kumpula.

CMS runs most jobs in Apptainer containers and this allows easier usage of different Linux distributions. Using containers gives improved I/O performance compared to fully virtualized services. The CMS Linux clusters are connected to the WLCG with Advanced Resource Connector (ARC) Compute Elements called kale-cms (600 cores, ARC 6) and alcyone-cms (160 cores, to be increased to 1024 cores, ARC 7). ARC middleware usage in CMS was piloted at HIP and has spread to several CMS sites in several different countries. The Linux clusters are managed with the OpenHPC provisioning tool. The CMS clusters in Helsinki are both connected with 10 Gb/s each to FUNET. The University of Helsinki is procuring a new HPC system that is planned to be used also for CMS computing when it becomes available in 2026.

The CMS 3400 TB dCache storage is hosted by CSC in Kajaani and connected with a 100 Gb/s link to the FUNET, the Nordic LHC network, the LHC OPN and the LHCOne networks. The supported protocols are XRootD and WebDAV.

The long term CMS computing challenge is to develop the computing model, software, grid middleware and cloud services needed to meet the significant increase in data produced by the luminosity increase after LS3.