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Distributed Computing and Data Analysis for CMS in view of the LHC startup

Distributed Computing and Data Analysis for CMS in view of the LHC startup. Peter Kreuzer RWTH-Aachen IIIa. International Symposium on Grid Computing (ISGC) Taipei, April 9, 2008. Outline. Brief overview of Worldwide LHC Grid: WLCG Distributed Computing Challenges at CMS Simulation

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Distributed Computing and Data Analysis for CMS in view of the LHC startup

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  1. Distributed Computing and Data Analysis for CMS in view of the LHC startup Peter Kreuzer RWTH-Aachen IIIa International Symposium on Grid Computing (ISGC) Taipei, April 9, 2008

  2. Outline • Brief overview of Worldwide LHC Grid: WLCG • Distributed Computing Challenges at CMS • Simulation • Reconstruction • Analysis • The physicist view • The road to the LHC startup Peter Kreuzer - CMS Computing & Analysis

  3. (x 10) (x 10) • Since 20 years the amount of Data and of Physicists per experiment grew drastically From local to distributed Analysis • Before : centrally organised Analysis • Example CMS :4-6 PBytes data per year, 2900 scientists, 40 countries, 184 institutes ! • Solution : ´´Tiered´´ Computing Model Peter Kreuzer - CMS Computing & Analysis

  4. Level of distribution motivated by the desire to leverage and empower resources + share load, infrastructure and funding Worldwide LHC Computing GRID • Tier-0 at CERN • Prompt Reconstruction • Calibration and Low • latency work • Archiving • 1.0 GByte/s • Tier-1s at large national • labs or universities • Re-Reconstruction • Physics ´skimming´ • Data Serving • Archiving Aggregate Rate from CERN to Tier-1s  > 1.0 GByte/s • Transfer Rate • to Tier-2 • 50-500 MBytes/s • Tier-2s primarily at Universities • Simulation • User Analysis • Tier-3s at Institutes with • modest Infrastructure • Local User Analysis • Opportunistic Simulation Peter Kreuzer - CMS Computing & Analysis

  5. WLCG Infrastructure • EGEE Enabling Grid for E-Science • OSG Open Science Grid 1 Tier-0 + 11 Tier-1 + 67 Tier-2 CMS : 1 Tier-0 + 7 Tier-1 + 35 Tier-2 Tier-0 -- Tier-1: dedicated 10Gbs Optical Network Peter Kreuzer - CMS Computing & Analysis

  6. Examples of Sites • T2 RWTH (Aachen) • CPU : 540 KSI2k = 360 cores • Disc : 100TB • Network (WAN): 2Gbit/sec • (2009 : 450 cores & 150TB) • T1 ASGC • CPU: 2.4 MSI2k ~1800 cores • Disc : 930TB  1.5PB • Tape : 586TB  800TB  • Network : 10Gbit/sec • T2 Taiwan • CPU :150 KSI2k • Disc : 19TB  62TB • Network : up to10Gbit/sec Peter Kreuzer - CMS Computing & Analysis

  7. Tier-2 Tier-1 CERN Pledged WLCG Resources 250,000 cores 2008 : 66,000 cores (Tape Storage = 33 PBytes in 2008)  CPU MSI2k • 1MSI2K = 670 cores 2008 : 40 PetaBytes Disc Storage  PetaBytes Peter Kreuzer - CMS Computing & Analysis (Reference : LCG Project Planning – 1.3.08)

  8. Challenges for Experiments :Example CMS • Scale-up and test distributed Computing Infrastructure • Mass Storage Systems and Computing Elements • Data Transfer • Calibration and Reconstruction • Event ´skimming´ • Simulation • Distributed Data Analysis • Test CMS Software Analysis Framework • Operate in quasi-real data taking conditions and simulateously at various Tier levels  Computing & Software Analysis (CSA) Challenge Peter Kreuzer - CMS Computing & Analysis

  9. CMS Computing and Software Analysis Challenges • CMS Scaling-up in the last 4 years Test (year) Goal : Jobs/day Scale • DC04 : 15,000 5% • 2005 - 2006 : New Data Model and New Software Framework • CSA06 : 50,000 25% • CSA07 : 100,000 50% • CSA08 : 150,000 100% • Requires 100s M simulated events input ? Peter Kreuzer - CMS Computing & Analysis

  10. The CSA07 data Challenge 100M Simulated Data Reconstruction100Hz TIER-0 CASTOR HLT CAF Calibration& Express Analysis 300MB/s Re-Reconstruction Skimms25k jobs/day TIER-1 TIER-1 TIER-1 TIER-1 20-200MB/s ~10MB/s TIER-2 TIER-2 TIER-2 TIER-2 Analysis 75k jobs/day Simulation 50M evt/month Peter Kreuzer - CMS Computing & Analysis

  11. In this presentation • Mainly covering CMS Simulation, Reconstruction and Analysis challenges • Data transfers challenges covered in talk by Daniele Bonacorsi during this session Peter Kreuzer - CMS Computing & Analysis

  12. CMS Simulation System CMS Physicist << Please simulate new physics >> << Where are my data ? >> Tier-1 Global Data Bookkeeping (DBS) Tier-2 ProdAgent ProdRequest Tier-2 Production Manager Tier-2 Tier-2 ProdAgent ProdAgent Tier-2 Tier-2 GRID Tier-2 Tier-2 Peter Kreuzer - CMS Computing & Analysis

  13. Local DBS Local DBS Processing Merging Tier-1 Tier-1 SE ProdAgent SE ProdAgent Merging Grid WMS Processing Tier-2 Grid WMS SE Tier-2 SE Merging Tier-2 SE Processing PhEDEx Large output file from Merge job Tier-2 SE Small output file from Processing job ProdAgent workflows 2) Merging: 1) Processing: • Data processing / bookkeeping / tracking / monitoring in local-scope • Output promoted to global-scopeDBS & Data transfer system PhEDEx • Scaling achieved by running in parallel multipleProdAgent instances Peter Kreuzer - CMS Computing & Analysis

  14. CMS Simulation Performance ~250M Events in 5 months • Tier-2 alone ~72% • OSG alone ~ 50% (Overall 07-08: 450M) • 20k jobs/day reached • < Job efficiency > ~ 75% June – November 2007 M Evts / Month Production Rate x 1.8 70 60 50 40 30 Peter Kreuzer - CMS Computing & Analysis Jul Jan Oct Apr

  15. Utilization of CMS Resources • average ~50% • In best productions periods 75% Missing Requests 5000 job- slots June – November 2007 Peter Kreuzer - CMS Computing & Analysis

  16. CSA07 Simulation lessons • Major boost in scale and reliability of production machinery • Still too many manual operations. From 2008 on: • Deploy ProdManager component (in CSA07 was ´human´ !) • Deploy Resource Monitor • Deploy CleanUpSchedule component • Further improvments in scale and reliability • gLite WMS bulk submission : 20k jobs/day with 1 WMS server • Condor-G JobRouter + bulk submission : 100k jobs/day and can saturate all OSG resources in ~1 hour. • Threaded JobTracking and Central Job Log Archival • Introduced task-force for CMS Site Commissioning • help detect site issues via stress-test tool (enforce metrics) • couple site-state to production and analysis machinery • Regular CMS Site Availability Monitoring (SAM) checks Peter Kreuzer - CMS Computing & Analysis

  17. CMS Site Availability Monitoring Availability Ranking (ARDA ´Dashboard´) 03/22/08 04/03/08 0% 100% • Important tool to protect CMS use cases at sites Peter Kreuzer - CMS Computing & Analysis

  18. CSA07 Reconstruction & Skimming 0) preparation of ´´Primary Datasets´´ mimics real CMS Detector+ Trigger data 1) Archive and Reconstruction at CERN T0 2) Archive and Re-Reconstruction at T1s 3) Skimming at T1s 4) Express analysis & Calibration at CERN Analysis Facility  3 different calibrations 10pb-1,100pb-1, 0pb-1 Peter Kreuzer - CMS Computing & Analysis

  19. Produced CSA07 Data Volumes x1e+8 DIGI-RAW-HLT-RECO events Total CSA07 event counts: 80M GEN-SIM 80M DIGI-RAW 80M HLT 330M RECO (3 diff. calibrations) 250M AOD 100M skims --------------------------- 920M events 10/’07 02/’08 • Total Data volume: ~2PB • Corresponds to expected 2008 volume ! CMS data in CASTOR@CERN: 3.7PB Peter Kreuzer - CMS Computing & Analysis

  20. CSA07 Reconstruction lessons 2k running jobs T0 and T1 processing • T0 Reconstruction at 100Hz only in bursts, mainly due to stream splitting activity • Heavy load on CASTOR • Usefull feedback to ProdAgent Developpers to prepare 2008 data taking (repacker, …) • T1 Processing : submission rate was main limitation. Now based on gLite bulk submission and reaching 12-14k jobs/day with 1 ProdAgent instance • Further rate improvment to be expected with T1 resource up-scaling Peter Kreuzer - CMS Computing & Analysis

  21. CMS Analysis System CRAB = CMS Remote Analysis Builder An interface to the GRID for CMS physicists Challenge : match processing resources with large quantities of data = ´´chaotic´´ Processing Tier-1 Tier-2 Global Data Bookkeeping (DBS) << Please analyse datasets X/Y >> CMS Physicist Tier-2 CRAB << Where are my jobs ? >> Tier-2 Tier-2 CRAB Server Tier-2 Tier-2 GRID Tier-2 Tier-2 Peter Kreuzer - CMS Computing & Analysis

  22. CRAB Architecture • Easy and transparent means for CMS users to submit analysis jobs via the GRID (LCG RB, gLite WMS, Condor-G) • CSA07 analysis: direct submission by user to GRID. Simple, but lacking automation and scalability •  2008 : CRAB server • Other new feature: local DBS for “private” users Peter Kreuzer - CMS Computing & Analysis

  23. Main causes: • data-access • remote stage out • manual user settings CSA07 Analysis • 100k jobs/day not achieved • mainly due to lacking data during the challenge • still limitted by data distribution: 55% jobs at 3 largest Tier-1s • and failure rate too high 53% Successful Jobs 20% failed Jobs 27% Unknown 20k jobs/day achieved + regularly ~30k/day JobRobot submissions Number of jobs Peter Kreuzer - CMS Computing & Analysis

  24. CMS Grid Users since 1 year • plot showing distinct users • 300 users during February 2008 • 20 most active users carry 1/3 of jobs Users Month CRAB Server Peter Kreuzer - CMS Computing & Analysis

  25. The Physicist View • SUSY Search in di-lepton + jets + MET • Goal : Simulate excess over Standard Model (´LM1´ at 1 fb-1) • Infrastructure • 1 desktop PC • CMS Software Environment (´CMSSW´ , ´CRAB´, ´Discovery´ GUI, …) • GRID Certificate + member of a Virtual Organisation (CMS) • Input data (CSA07 simulation/production) • Signal (RECO) : 120k events = 360 GB • Skimmed Background (AOD) : 3.3 M events = 721 GB • WW / WZ / ZZ / single top • ttbar / Z / W + jets • Unskimmed Background : 27 M events = 4 TB (for detailed studies only) • Location of input data • T0/T1 : CERN (CH), FNAL (US), FZK (Germany) • T2 : Legnaro (Italy), UCSD (US), IFCA (Spain) ~1.1 TB Peter Kreuzer - CMS Computing & Analysis

  26. GRID Analysis Result End-Point Signal • Analysis Latency • Signal + Bgd = • 322 jobs  22h to produce this result ! • Detailed studies = 1300 jobs  ~3.5 days Z peak from SUSY cascades [GeV] Georgia Karapostoli – Athens Univ. Peter Kreuzer - CMS Computing & Analysis

  27. CSA07 Analysis lessons • Improve Analysis scalability, automation and reliability • CRAB-Server • Automate job re-submission • Optimize job distribution • Decrease failure rate • Move Analysis to Tier-2s • To protect Tier-0/1 LSF and storage systems • To make use of all available GRID resources • Encourage Tier-2_to_Physics_group association • In close collaboration with sites • With solid overall Data Management strategy • Assess local scope DM for Physics groups & storage of user data • Aim for 500 users by June and exceed capacity of several gLite WMS Peter Kreuzer - CMS Computing & Analysis

  28. Goals for CSA08 (May ’08) • “Play through” first 3 months of data taking • Simulation • 150M events at 1 pb-1(“S43”) • 150M events at 10 pb-1 (“S156”) • Tier-0 : Prompt reconstruction • S43 with startup-calibration • S156 with improved calibration • CERN Analysis Facility (CAF) • Demonstrate low turn-around Alignment&Calibration workflows • Coordinated and time-critical physics analyses • Proof-of-principle of CAF Data and Workflow Managment Systems • Tier-1 : Re-Reconstruction with new calibration constants • S43 : with improved constants based on 1 pb-1 • S156 : with improved constants based on 10 pb-1 • Tier-2 : • iCSA08 simulation (GEN-SIM-DIGI-RAW-HLT) • repeat CAF-based Physics analyses with Re-Reco data ? Peter Kreuzer - CMS Computing & Analysis

  29. 2008 Detector installation, commissioning and operation Preparation of Software, Computing and Physics analysis 2007 Physics Analyses results Cooldown of magnet Private global runs (2 days/week) & Private mini-daq CCRC’08-1 GRUMM CMSSW 1.8.0 sample production CMSSW 2.0 release [production start-up MC samples] Low i test 2 weeks of 2.0 testing Beam-pipe baked-out Pixels installed CR 0T iCSA08 sample generation “CROT” CR 0T iCSA08 / CCRC’08-2 CMS closed pre CR 4T “CRAFT” CMSSW 2.1 release [all basic sw components ready for LHC, new T0 prod tools] Initial CMS ready for run CR 4T fCSA08 or beam! Must keep exercises mostly non-overlapped CCRC = Common-Vo Computing Readiness Challenge CR = Commissioning Run Peter Kreuzer - CMS Computing & Analysis

  30. Where do we stand ? • WLCG : major up-scaling since 2 years ! • CMS : impressive results and valuable lessons from CSA07 • Major boost in Simulation • Produced~2 PBytes data in T0/T1 Reconstruction and Skimming • Analysis : number of CMS Grid-users ramping up fast ! • Software : addressed memory footprint and data size issues • Further Challenges for CMS : scale from 50% to 100% • Simultaneous and continuous operations at all Tier levels • Analysis distribution and automation • Transfer rates (see talk by D.Bonacorsi) • Upscale and commission the CERN Analysis Facility (CAF) • CSA08, CCRC08, Commissioning Runs • Challenging and motivating goals in view of Day-1 LHC ! Peter Kreuzer - CMS Computing & Analysis

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