Speaker
Description
The Czech WLCG Tier-2 reliably delivers computing and storage pledges to the LHC experiments through a geographically distributed infrastructure. CZ-Tier-2 resources are deployed across three sites and interconnected by high-capacity links provided by the Czech NREN, CESNET. In addition, significant CPU capacity from the Czech national supercomputing center IT4I is integrated into WLCG operations via the main CZ-Tier-2 hub at FZU, which acts as the central distribution and data-exchange point.
To meet the increasing wide-area network (WAN) demands expected for HL-LHC, the external connectivity of the FZU site has undergone a major upgrade. During the WLCG Data Challenge in February 2024, the site operated with 100 Gbps connectivity to LHCONE complemented by a 40 Gbps generic Internet link. This has since evolved into a 400 Gbps LHCONE connection plus an additional 100 Gbps external link, enabling significantly higher throughput for data movement and remote access workflows.
In this contribution, we present a series of performance and stress tests of the LHCONE connection carried out shortly after the upgrade in 2025. The initial measurements were performed using available storage servers equipped with 2×25 Gbps network interfaces (or slower). We later complemented these tests with dedicated measurements from a single perfSONAR host equipped with a 400 Gbps NIC.
We demonstrate that CZ-Tier-2 can effectively exploit the upgraded connectivity. The results indicate that the site is well prepared for the increased WAN traffic and data distribution patterns anticipated in the HL-LHC era.