Worldwide LHC Computing Grid
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| Worldwide LHC Computing Grid | |
|---|---|
| Name | Worldwide LHC Computing Grid |
| Abbreviation | WLCG |
| Established | 2007 |
| Headquarters | Geneva |
| Coordinates | 46.2333° N, 6.0500° E |
| Parent | CERN |
Worldwide LHC Computing Grid
The Worldwide LHC Computing Grid is a global distributed computing infrastructure designed to process and analyse data from the Large Hadron Collider, linking major facilities such as CERN, Fermilab, SLAC National Accelerator Laboratory, DESY, and KEK. It supports experiments including ATLAS, CMS, ALICE, and LHCb and integrates resources from national laboratories, regional centres, and university clusters such as Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, Rutherford Appleton Laboratory, TRIUMF, and INFN. The Grid federates computing, storage, and networking from partners like GridPP, OSG (Open Science Grid), NorduGrid, EGI (European Grid Infrastructure), and NDGF to enable large-scale particle physics analysis.
Overview
The Grid provides a tiered service model aligning with the Tier-0 (CERN) concept, Tier-1 centres such as Centre de Calcul de l'IN2P3, and numerous Tier-2 university clusters including University of Oxford, University of Cambridge, University of Tokyo, McGill University, and University of Melbourne. It interacts with major networking backbones like GÉANT, Internet2, ESnet, REUNA, and SURFnet and uses protocols and middleware originating from projects such as gLite, ARC (Advanced Resource Connector), HTCondor, FermiGrid, and Globus Toolkit. Operational governance draws on bodies like WLCG Collaboration, CERN IT Department, EUROfusion-associated centres, and national funding agencies including EPSRC, DOE, NSF, ANR, and DFG.
Architecture and Components
The architecture combines compute farms, tape libraries, and disk caches provided by institutions including CNAF, CCIN2P3, PIC (Port d'Informació Científica), CYFRONET, and KISTI. Core software components include workload management systems such as PanDA, DIRAC, ARC Control Tower, and HTCondor-CE; data management systems like Rucio, DQ2 (historical), PhEDEx (historical), and SAMGrid; and monitoring stacks incorporating Grafana, Prometheus, Nagios, and ELK Stack. Storage technologies span dCache, EOS (CERN) , Lustre, ZFS, and magnetic tape systems from IBM and Oracle (StorageTek). Networking relies on optical infrastructure from providers such as Level 3 Communications, Orange S.A., Deutsche Telekom, and regional research networks including SURF, NORDUnet, and Canarie.
Operations and Resource Management
Operations use coordinated shifts and support rosters staffed by experts from CERN IT, ATLAS Experiment, CMS Experiment, ALICE Collaboration, LHCb Collaboration, and site teams at RAL, Fermilab, and TRIUMF. Resource brokerage integrates batch systems like SLURM, Torque, Grid Engine, and HTCondor with federated identity systems such as EduGAIN, CILogon, and VOMS; accounting aligns with metrics developed by WLCG Site Status Board and the Open Grid Forum. Incident response collaborates with organisations including FIRST (Forum of Incident Response and Security Teams), CERT-EU, US-CERT, DFRLab, and national Computer Emergency Response Teams like CERT-UK and CERT-FR.
Data Management and Workflows
Data flows from detectors via High-Level Trigger systems into tape-backed archives at Tier-0 and are replicated to Tier-1 centres such as SARA and PIC using transfer tools and protocols like FTS (File Transfer Service), GridFTP, HTTP/WebDAV, and xrootd. Workflow orchestration uses experiment-specific frameworks including Athena (software), CMSSW, AliRoot, and Gaudi integrated with workflow managers such as PanDA for ATLAS and CRAB for CMS, plus provenance systems inspired by PROV (W3C) concepts. Cataloguing utilises services influenced by CERN Open Metadata initiatives and metadata registries similar to Invenio and Dataverse used by research infrastructures like Zenodo and figshare for publication linking.
Security and Policy
Security architecture combines authentication and authorization via X.509 certificates, OAuth 2.0, and federated identity providers including eduGAIN members and national federations such as UK Access Management Federation and DFN-AAI. Policy frameworks reference best practices from ISO/IEC 27001, compliance interactions with funding agencies like European Research Council, and coordination with legal entities including European Commission DG CONNECT. Security operations coordinate with CERN Computer Security Team, regional CERTs such as CERT-BE and CERT-DE, and international initiatives such as ENISA and INTERPOL for threat intelligence sharing.
History and Development
Origins derive from early Grid projects including DataGrid, European DataGrid, LHC Computing Grid Project, and collaborations with Globus Project, GriPhyN, and OpenGridForum. Major milestones include commissioning during the first LHC run with analyses by ATLAS and CMS that contributed to the Higgs boson discovery, expansions driven by detector upgrades for LHC Run 2 and Run 3, and transitions from legacy middleware such as gLite to modern systems like Rucio. Funding and technical evolution involved agencies and programmes including FP6, FP7, Horizon 2020, STFC, DOE Office of Science, and national initiatives like CERN-EU Cooperation. Influential individuals and teams came from laboratories such as CERN, SLAC, Brookhaven National Laboratory, and universities including University of Manchester and University of California, Berkeley.
Impact and Collaboration Challenges
The Grid catalysed advances used by projects beyond particle physics, influencing infrastructures for Square Kilometre Array, European Space Agency, Human Brain Project, Climate modelling consortia, and collaborations with industry partners like IBM, HP, Dell EMC, and Google Cloud. Challenges include scaling to exabyte datasets arising from detector upgrades, integrating commercial cloud providers such as Amazon Web Services, Microsoft Azure, and Google Cloud Platform while maintaining provenance and reproducibility standards promoted by FAIR data principles and organisations like RDA (Research Data Alliance. Governance and collaboration confront cross-border funding, intellectual property, and technical harmonisation across institutions like CERN Council, European Research Area, National Science Foundation, and national ministries of research.