The National Laboratory of Frascati’s Tier2 is one of the data centres comprising the WLCG (Worldwide LHC Computing Grid), the largest existing computational grid. WLCG is a global infrastructure implemented in order to provide computing resources to store, distribute and analyse about 30 Petabytes (30 million Gigabytes) of data generated each year by the Large Hadron Collider (LHC) at CERN, making them available to all partners of the collaboration, regardless of their geographical location.WLCG is the result of a collaboration of national and international computing infrastructures coordinated by CERN and operated by an international collaboration of between the four LHC experiments (ALICE, ATLAS, CMS and LHCb) and of the participating computing centres.
42 countries, 170 computing centres, 2 million jobs executed each day.
The WLCG calculation allowed physicists to announce the discovery of the Higgs boson on 4 July 2012!
The WLCG infrastructure consists of multiple layers or tiers: 0, 1, 2, 3 with different service levels.
Tier0 is the CERN data centre, situated in Geneva and in the Wigner Research Centre in Hungary (connected with two dedicated 100 Gbit/s links), responsible for custody of the raw data and performing a first data reconstruction. The Tier1, 13 large computing centres with ample storage capacity, are responsible for a percentage of the data and perform large-scale computations. Finally, the Tier2, which store a part of the data, mainly provide computing power for analysis and the Monte Carlo simulation.
One of the Tier2, mainly dedicated to calculation for the ATLAS experiment, is hosted at the INFN National Laboratory of Frascati.
This centre, in addition to the ATLAS experiment, also supports the activities of other experiments, such as: KM3NeT, Belle II, the other LHC experiments and, within the scope of a collaboration between INFN and INAF, CTA (Cherenkov Telescope Array). The CTA project is in fact considered strategic for both institutions in the coming years, in order to develop in synergy calculation-related aspects, integrating the different skills and experience in managing large computing infrastructures (INFN) and implementing software for data analysis and astronomy archive and database management (INAF). Therefore, in succession, the following calculation requirements will be addressed: prototype of the Small Size Dual Mirror Telescope (SST-2M) within the scope of Astri, the mini Array of Small Size Dual Mirror Telescopes within the scope of CTA and, finally, the CTA Data Centre; to this end, integration of the software and the archive, developed by INAF-Astronomical Observatory of Rome, in the Tier2 calculation infrastructure of the Laboratories, has begun.
Finally, Tier 2 also includes a number of initiatives useful for the calculation of local groups and of the ATLAS collaboration, for example:
- participation in the management of the ATLAS Virtual Organization (defined as the set of resources, people and policies of the entire experiment community),
- participation in the development and testing of the DPM (Disk Pool Manager) software: a software for storage system management in the Grid,
- study, testing and promotion of a tool for distributed analysis, such as PROOF on Demand (PoD) which allows users to use (non-dedicated) computing resources in Grid for on-demand instancing of a cluster for analysis with PROOF;
in addition to managing local computing resources for the different needs of ATLAS users in Frascati.