An introduction to the ATLAS Computing Model Alessandro De Salvo <Alessandro.DeSalvo@roma1.infn.it> 20-02-2008 Outline The ATLAS Tier and Cloud model The Tier centers Data types Data avilability in the Tiers A. De Salvo – 20 Apr 2008

The ATLAS Tier and Cloud Model Multi-Tier gerarchical model Cloud model Each Tier 1 center defines a Cloud 3 or 4 Tier2 centers are associated to each Cloud (Tier1), often on the basis of a geographical criteria

The ATLAS Tier1 centers ASGC (Taiwan) BNL (USA) CNAF (Italy) AU-ATLAS, TW-FTT,AU-UNIMELB BNL (USA) AGLT2, BU, MWT2, OU, SLAC, UTA, WISC CNAF (Italy) LNF, MILANO, NAPOLI, ROMA1 FZK (Germany) CSCS,CYF,DESY-HH,DESY-ZN,FZU,LRZ, FREIBURG, WUP NDGF (Nordic Countries) LYON (France) BEIJING, CPPM, LAL, LAPP, LPC, LPNHE, NIPNE_02,NIPNE_07, SACLAY,TOKYO PIC (Spain) IFAE, IFIC, UAM,LIP RAL (UK) GLASGOW, LANCS, MANC, QMUL, DUR, EDINBURGH, OXF,CAM,LIV,BRUN,RHUL SARA (Netherlands) IHEP, ITEP, JINR, PNPI, SINP TRIUMF (Canada) ALBERTA, MONTREAL, SFU, TORONTO,UVIC

Tasks of the Tier centers Raw data archival Data distribution to the Tier1 centers Prompt Reconstruction of the raw data within 48 hours 1st pass calibration within 24 hours Distribution of the reconstruction output to the Tier1 centers ESD, AOD and TAG Tier-1 Long-term access and storage of a subset of the raw data Backup copy of part of the raw data of another Tier1 Reprocessing of the raw data stored in each Tier1 with the final calibration and alignment parameters, after 2 months of the data taking AOD distribution to the Tier2 centers Archival of the MC data produced in the Tier2 centers Group analysis Centralized analysis of the physics groups Tier-2 Monte Carlo simulation User analysis Off-site detector calibration (selected Tier2s only)

Data types and sizes Raw data ESD (Event Summary Data) Byte-stream data coming from the trigger ESD (Event Summary Data) Output of the reconstruction Tracks Hits Calorimeter clusters Combined reconstruction objects … Used for calibration, alignment, refitting Generally used when the data in the AOD is not sufficient to complete the analysis AOD (analysis Object Data) Reduced format created for the analysis Reconstructed physical quantities Electrons, muons, taus, … DPD (Derived Physics Data) Reduced data for explicit usage in ROOT 1.6 MB Target 500 kB Currently 750/900 kB Target 100 kB Currently 250/290 kB 10% of AOD

Event size

Data distribution

Tier-0 throughput schema TDAQ output rate = 320 MB/s ⇒ 200 Hz (trigger rate) · 1,6 MB (event size) Dedicated optical-fiber connection Tier0 ↔ Tier-1s @ 10 Gbps

The Tier-0 center The full set of RAW data and the primary ESD and AOD are stored at Tier-0

The Tier-1 centers

Tier-1 data and computing activities A full copy of the RAW data in the Tier-1 centers (10% on disk) Double-copy of the ESD dta in the Tier-1 centers A full copy of AOD and TAG in each Tier-1 Each Tier-1 reprocesses its own RAW data and replicates them A full copy of physics group DPD per Tier-1 Computing activities (2008) 25% reprocessing 25% simulation 50% group analysis

The Tier-2 centers

Tier-2 data and computing activities A full copy of the AOD and TAG data in each Tier-2 cloud Physiscs group DPD and user DPD RAW data in all the Tier-2 centers 30% in 2008 10% in 2009 ESD data in all the Tier-2 centers 50% in 2008 30% in 2009 Computing activities (2008) 15% reconstruction 37% simulation 48% user analysis