The ATLAS Computing Model and USATLAS Tier-2/Tier-3 Meeting Shawn McKee University of Michigan Joint Techs, FNAL July 16 th, 2007

The ATLAS Computing Model and USATLAS Tier-2/3 Meeting Shawn McKee 2 Overview  The ATLAS collaboration has only ~year before it must manage large amounts of “real” data for its globally distributed collaboration.  ATLAS physicists need the software and physical infrastructure required to:  Calibrate and align detector subsystems to produce well understood data  Realistically simulate the ATLAS detector and its underlying physics  Provide access to ATLAS data globally  Define, manage, search and analyze data-sets of interest  I will give a quick view of ATLAS plans & highlight the processing workflow we envision. This will be brief; most info is available from our recent USATLAS Tier-2/3 meeting presentations ATLAS

Shawn McKee 3 The ATLAS Computing Model  Computing Model is well evolved and documented in C-TDR  pdf pdf  There are many areas with significant questions/issues to be resolved:  Calibration and alignment strategy is still evolving  Physics data access patterns partially exercised  Unlikely to know the real patterns until 2008!  Still uncertainties on the event sizes, reconstruction time  How best to integrate ongoing “infrastructure” improvements from research efforts into our operating model?  Lesson from the previous round of experiments at CERN (LEP, )  Reviews in 1988 underestimated the computing requirements by an order of magnitude! The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

 We have a hierarchical model (EF-T0-T1-T2) with specific roles and responsibilities  Data will be processed in stages: RAW->ESD->AOD->TAG  Data “production” is well-defined and scheduled  Roles and responsibilities are assigned within the hierarchy.  Users will send jobs to the data and extract relevant data  typically DPD’s (Derived Physics Data) or similar  Goal is a production and analysis system with seamless access to all ATLAS grid resources  All resources need to be managed effectively to insure ATLAS goals are met and resource providers policy’s are enforced. Grid middleware must provide this Shawn McKee 4 ATLAS Computing Model Overview The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

 Event Filter Farm at CERN  Assembles data (at CERN) into a stream to the Tier 0 Center  Tier 0 Center at CERN  Data archiving: Raw data to mass storage at CERN and to Tier 1 centers  Production: Fast production of Event Summary Data (ESD) and Analysis Object Data (AOD)  Distribution: ESD, AOD to Tier 1 centers and mass storage at CERN  Tier 1 Centers distributed worldwide (10 centers)  Data steward: Re-reconstruction of raw data they archive, producing new ESD, AOD  Coordinated access to full ESD and AOD (all AOD, % of ESD depending upon site)  Tier 2 Centers distributed worldwide (approximately 30 centers)  Monte Carlo Simulation, producing ESD, AOD, ESD, AOD sent to Tier 1 centers  On demand user physics analysis of shared datasets  Tier 3 Centers distributed worldwide  Physics analysis  A CERN Analysis Facility  Analysis  Enhanced access to ESD and RAW/calibration data on demand Shawn McKee 5 ATLAS Facilities and Roles The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

Shawn McKee 6 USATLAS Tier-2/Tier-3 Meeting  In mid June 2007 we held our first joint USATLAS Tier-2/Tier-3 Meeting  Hosted at Indiana University (Bloomington)  June nd 2007  Indico has the agenda and talks available:   The first half of the meeting focused on Tier-3 concerns  Second half was concentrated on Tier-2 issues and planning  See slides from Amir Farbin which provide a very good overview of the analysis needs from the point of view of a physicist.  mp;resId=0&materialId=slides&confId= mp;resId=0&materialId=slides&confId= mp;resId=0&materialId=slides&confId=15523  mp;resId=0&materialId=slides&confId= mp;resId=0&materialId=slides&confId= mp;resId=0&materialId=slides&confId=15523 The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

The ATLAS Computing Model: Status, Plans and Future Possibilities Shawn McKee 7 Slide From Amir Farbin

Shawn McKee 8 ATLAS Resource Requirements in for 2008 Recent (July 2006) updates have reduced the expected contributions Computing TDR The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

Slide From Amir Farbin

The ATLAS Computing Model: Status, Plans and Future Possibilities Shawn McKee 10 Slide From Amir Farbin

Network and Resource Implications  The ATLAS computing model assumes 12 Tier-2 “cores” per physicist  This won’t be able to provide a timely turn-around for most analysis work.  Assumption is Tier-3 should additionally provide 25 more cores and around 50TB/year  Networks for “Tier-3” scale analysis should provide ~10MBytes/sec per core  Typical 8 core machine requires gigabit “end-to-end” connectivity; but in bursts  Will Tier-2’s and Tier-3 have sufficient useable bandwidth (end-to-end issues)? Shawn McKee 11 The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

Planning for 2008  To date most requirements envisioned for LHC scale physics from the network have yet to be realized.  Once real data is flowing this will change quickly  End-sites (Tier-2 or Tier-3) must be ready to accommodate needs  Physicist’s will need very high network performance in “bursts”.  Ideally a multiplexed form of network access/usage could provide sufficient capabilities.  End-to-end issues will need to be addressed Shawn McKee 12 The ATLAS Computing Model and USATLAS Tier-2/3 Meeting

 Within a year real LHC data will begin flowing  Physicists globally will be intently working to access and process data…there will be implications for networks, storage systems and computing resources.  Planning should provide for reasonable network infrastructure:  Typical Tier-2: 10+ Gbps  Typical Tier-3: 1 (to 10) Gbps (depends on number of physicists and size of resources)  Network services incorporated from research areas may be needed to insure end-to-end capabilities and effective resource management  Shortly we will be living in “Interesting Times”… Conclusions Shawn McKee 13 The ATLAS Computing Model and USATLAS Tier-2/3 Meeting