Grid computing at CERN

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Grid computing at CERN

• Oxana Smirnova
• Lund University/CERN
• 2nd NGN meeting, Tallinn, January 20, 2005

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CERN the European Particle Physics Lab
Large Hadron Collider Worlds biggest
accelerator at CERN
http//www.cern.ch
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Collisions at LHC
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Experiments at LHCand computing challenges

• Data-intensive tasks
• Large datasets, large files
• Lengthy processing times
• Large memory consumption
• High throughput is necessary
• Very distributed user base
• 50 countries, thousands of researchers
• Distributed computing resources of modest size
• Produced and processed data are hence
  distributed, too
• Issues of coordination, synchronization and
  authorization are outstanding

HEP community at CERN were the first to recognize
the necessity of Grid computing
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Grid projects at and around CERN

• MONARC project developed a multi-tiered model for
  distributed analysis of data
• Particle Physics Data Grid (PPDG) and GriPhyN
  projects by US physicists started using Grid
  technologies
• Used parts of the Globus Toolkit
• Globus was picked up by the CERN-lead EU DataGrid
  (EDG) project
• EDG did not satisfy production-level
  requirements many simpler solutions appeared
  (still, Globus-based)
• NorduGrid (Northern Europe and others)
• Grid3 (USA)
• EGEEs gLite (EU, prototype)
• LHC Computing Grid (LCG) builds Grid for CERN,
  uses modified EDG and aims towards gLite

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LHC experiments usage of Grid

• The experiments recently presented their
  computing models
• All rely on Grid computing in many aspects
• Common points
• Multi-tiered hierarchy
• Tier0 (CERN) ? Tier1 (regional) ? Tier2 (local)
• Raw and reconstructed data 2-3 copies worldwide,
  analysis objects a copy per Tier1, some at Tier2
  (dedicated)
• Grid(s) to be used to manage centralized
  production at Tier2s and processing at Tier1s,
  and eventually for analysis
• Differences
• 3 out of 4 use different non-LCG Grid-like
  solutions
• ALICE AliEn (assume it will transform into
  gLite)
• ATLAS Grid3, ARC
• LHCb Dirac
• Only ALICE makes explicit statement on the Grid
  middleware (needs AliEn)
• Some see Grid as a necessity, others as a
  possible optimization
• Some require a single Grid, others realize there
  will be many

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LCG the central Grid project for CERN

• Sometimes referred to as the fifth LHC
  experiment
• Major activities (see http//cern.ch/lcg)
• Fabric
• Grid deployment and operations
• Common applications
• Distributed data analysis (ARDA)
• Originally, have chosen EDG as the basic
  middleware
• Applies some modifications uses only selected
  services
• Took over EDG middleware support
• Later, agreed to share some operational
  responsibilities and middleware with EGEE
• CERN is actually the coordinator of EGEE (see
  http//cern.ch/egee)
• EGEEs gLite middleware is expected to inherit
  many EDG solutions
• Since late 2003, LCG is in the production mode,
  to be used by the LHC experiments
• 80 sites, 7000 processors

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LCG status today

• LCG Comprehensive Review took place on November
  22-23, 2004
• Materials publicly available at
  http//agenda.cern.ch/fullAgenda.php?idaa043872
• Excerpts from the final report (from slides by
  K.Bos)
• Middleware Progress was reported in the
  development and use of the middleware but the
  LHCC noted outstanding issues concerning the
  LCG-2 low job success rate, inadequacies of the
  workload management and data management systems,
  as well as delays in the release of the EGEE
  gLite services. Continued delays in gLite may
  hinder future progress in ARDA. LCG-2 has been
  used as a production batch system, but Grid-based
  analysis of the simulated data is only just
  starting. The interoperability of the various
  types of middleware being produced should be
  pursued together with common interface tools, and
  developers of the gLite middleware should remain
  available for the support phase.
• Grid Deployment and Regional Centers Good
  progress was reported on the installation of Grid
  software in remote sites. A large amount of data
  has been processed on the LCG-2 Grid as part of
  the Data Challenges and the LCG-2 Grid has been
  operated successfully for several months.
  However, the LHCC noted that the service provided
  by LCG-2 was much less than production quality
  and the experiments and LCG Project expended a
  large amount of effort to be in a position to use
  the service.

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LCG status, continued

• Excerpts from the final report, continued
• Fabric and Network The LHCC has no major
  concerns regarding the Fabric Area and Wide Area
  Networking. In view of the reported delays, the
  Committee will continue checking on the
  availability and performance of the CASTOR disk
  pool management system.
• Applications area The LHCC noted the good
  progress in the Applications Area with all
  projects demonstrating significant steps in the
  development and production of their respective
  products and services. The major outstanding
  issues lie with the insufficient coordination
  between the Applications Area and ROOT and with
  the imminent reduction of manpower due to the
  transition from the development to the
  deployment, maintenance and support phases.
• Management and Planning The LHCC took note of
  the upcoming milestones for the LCG and noted
  that discussions are currently underway to secure
  the missing manpower to develop, deploy and
  support the Grid services. The lines of
  responsibility and authority in the overall
  organization structure need further
  clarification.

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Plans for the gLite middleware in 2005

• End of March
• use the gLite middleware (beta) on the extended
  prototype (eventually the pre-production service)
  (beta) and provide feedback (technical issues and
  collect high-level comments and experience from
  the experiments)
• Release Candidate 1
• End of June
• use the gLite middleware (version 1.0) on the
  extended prototype (eventually the pre-production
  service) and provide feedback (technical issues
  and collect high-level comments and experience
  from the experiments)
• Release 1
• End of September
• use the gLite middleware (version 1.1) on the
  extended prototype (eventually the pre-production
  service) and provide feedback (technical issues
  and collect high-level comments and experience
  from the experiments)
• Interim Integrated Build
• End of December
• use the gLite middleware (version 1.2 - release
  candidate 2) on the extended prototype
  (eventually the pre-production service) and
  provide feedback (technical issues and collect
  high-level comments and experience from the
  experiments)
• Release Candidate 2

Slide by F.Hemmer
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LCG planning in 2005

• February/March Fabric Grid workshop on the
  computing models
• First quarter 2005
• Improve/work out relations between Tier0/1/2
• Understand data access patterns, define
  experiments shares at Tier1s
• Prepare documentation for MoUs between LCG and
  Tier0/1/2 centers
• Work on Technical Design Report
• Other
• March detailed plan for the service challenges
• March phase 2 Applications Area plan
• April initial plan for Tier-0/1/2 networking
• April prepare final version of the LCG MoU
• May proposal for middleware evolution
• End June Technical Design Report
• Detailed plan for installation and commissioning
  the LHC computing environment
• September final installation and commissioning
  plan
• October ready to sign the MoU

Based on slides by L.Robertson
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Summary

• CERN expects LCG to provide adequate Grid-like
  computing infrastructure for the future LHC data
  processing
• The resources are available, and the owners will
  sign MoUs with CERN/LCG in 2006
• The experiments were testing extensively the LCG
  system throughout 2004
• No satisfactory production-level service
• No optimization yet, needs tremendous efforts to
  keep it running
• Other Grid solutions offered less resources but
  better reliability with less efforts (see e.g.
  talks at CHEP04)
• Major problems
• Operational and organizational issues
• Inadequate middleware without official
  developers support
• EGEE is expected to help out
• Manpower for operation, infrastructure and
  support centers
• Improved middleware (gLite)
• Still, it becomes clear that there will be no
  single Grid solution for CERN
• EDG/LCG, AliEn, gLite, Dirac, Grid3/OSG,
  NorduGrids ARC, INFN-Grid and counting all are
  being used and have avid supporters
• Some expect LCG to concentrate on fabric,
  operations and applications