HPC resources for CMS offline computing: An integration and scalability challenge for the Submission Infrastructure

TL;DR

This paper discusses integrating HPC resources into the CMS offline computing infrastructure to address future scalability challenges posed by increasing computational demands and resource diversity at the LHC.

Contribution

It presents the integration approach of HPC resources into CMS computing and reports scalability testing results to ensure future infrastructure growth.

Findings

Successful integration of HPC resources into CMS infrastructure.

Scalability tests indicate the potential to support future computing demands.

Identified challenges in maintaining flexibility and efficiency at larger scales.

Abstract

The computing resource needs of LHC experiments are expected to continue growing significantly during the Run 3 and into the HL-LHC era. The landscape of available resources will also evolve, as High Performance Computing (HPC) and Cloud resources will provide a comparable, or even dominant, fraction of the total compute capacity. The future years present a challenge for the experiments' resource provisioning models, both in terms of scalability and increasing complexity. The CMS Submission Infrastructure (SI) provisions computing resources for CMS workflows. This infrastructure is built on a set of federated HTCondor pools, currently aggregating 400k CPU cores distributed worldwide and supporting the simultaneous execution of over 200k computing tasks. Incorporating HPC resources into CMS computing represents firstly an integration challenge, as HPC centers are much more diverse compared to Grid sites. Secondly, evolving the present SI, dimensioned to harness the current CMS computing capacity, to reach the resource scales required for the HLLHC phase, while maintaining global flexibility and efficiency, will represent an additional challenge for the SI. To preventively address future potential scalability limits, the SI team regularly runs tests to explore the maximum reach of our infrastructure. In this note, the integration of HPC resources into CMS offline computing is summarized, the potential concerns for the SI derived from the increased scale of operations are described, and the most recent results of scalability test on the CMS SI are reported.