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BaBar Grid

BaBar Grid. Tim Adye Particle Physics Department Rutherford Appleton Laboratory PP Grid Team Coseners House 8 th November 2002. Talk Plan. BaBar distributed computing model RAL Tier A Remote job submission BaBar VO and Authorisation Metadata Data distribution.

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BaBar Grid

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  1. BaBar Grid Tim Adye Particle Physics Department Rutherford Appleton Laboratory PP Grid Team Coseners House 8th November 2002 Tim Adye

  2. Talk Plan • BaBar distributed computing model • RAL Tier A • Remote job submission • BaBar VO and Authorisation • Metadata • Data distribution Tim Adye

  3. The BaBar Collaboration 9 Countries 74 Institutions 566 Physicists Tim Adye

  4. LER (e+, 3.1 GeV), I(e+ )=2.1 A Linear Accelerator HER (e-, 9.0 GeV), I(e- )=1.0 A BaBar BABAR PEP-II ring: C=2.2 km May 26, 1999: 1st events recorded by BaBar PEP-II e+e- Ring and BaBar Detector

  5. BaBar’s Distributed Computing Model • Goal is to spread computing load much more around the collaboration • Simulation production is already distributed – 75% in the UK! • Now have three new “Tier A” centres • Lyon – Objectivity (database) analysis (since last year) • RAL – Kanga (ROOT microDST) analysis (from May 2002) • Padova – Reprocessing (just starting) • Also several “Tier C” sites (ie. Universities, 9 in UK) • Analysis data format (Kanga vs Objectivity) is a matter of heated debate at the moment • Whatever the future of Objectivity, Kanga(championed in UK/Germany) looks set to continue Tim Adye

  6. RAL Tier A • UK MoU with BaBar reduces our common fund contributions in exchange for providing Tier A facility • RAL has now relieved SLAC of all Kanga analysis • Impressive takeup from UK and non-UK users • See Andrew’s talk • It is the primary repository of Kanga data • ~20 TB on disk • BaBar analysis environment tries to mimic SLAC so external users feel at home • Grid job submission should greatly reduce this requirement Tim Adye

  7. Remote Job SubmissionShort term (this month!) • Allow SLAC or University users to submit BaBar analysis jobs to RAL or Lyon Tier A sites from their home machines • dg-job-submit • Simplifies local development and debugging, while providing access to full dataset and large CPU farms • RAL vs IN2P3 selected explicitly by user • “canned” JDLRequirements; dataset selection left to user • Why couldn’t we do this a year ago? • BaBar authorisation (see later) • Gatekeeper needed to be able to submit to production farm • Define which BaBar configuration files to send with job • Developed a procedure to merge all tcl files into one • Resource Broker reliability – better with EDG 1.2. Tim Adye

  8. Remote Job SubmissionMedium term (early next year) • Allow remote submission to UK Farms and SLAC • In principle this is already set up • Select site (CE) based on user requirements • Eg. Dataset available, software release, etc. • Split job between sites based on available datasets • Already have demonstrator for a canned analysis job • http://www.hep.man.ac.uk/groups/slacb/gridtest.html Tim Adye

  9. BaBar VO and Authorisation • Use certificates from EDG and ESnetCAs for authentication • Authorisation required to identify BaBar users • Provides access to BaBar-specific facilities and environment • Cannot maintain grid-mapfile by hand • Doesn’t scale to 1202+ users • Use existing SLAC BaBar user registration • User provides certificate id at SLAC • Automatic procedure checks AFS group and fills VO • CEs use VO for authorisation • Naturally handles people leaving the experiment Tim Adye

  10. Analysis Metadata • Currently have about a million Kanga files in a deep directory tree • Need a catalogue to facilitate data distribution and allow analysis datasets to be defined. • SQL database • Locates ROOT files associated with each dataset • Selections based on decay channel, run range, beam energy, reconstruction processing version, etc. • Each site has its own (MySQL or Oracle) database • Includes a copy of SLAC database with local information (eg. files on local disk, files to import, local tape backups) • Some use of SRB for local Objectivity metadata at SLAC and Lyon Tim Adye

  11. Data Distribution • Kanga and Objectivity distribution currently handled by homegrown procedures • Use bbftp. bbcp soon. Will look at GridFTP • Next step is to run transfers using Grid job submission • Web control pages under development • Authorisation done using Grid certificates • Looking at SRB and RLS for data distribution Tim Adye

  12. Summary • BaBar already has a highly distributed analysis environment • RAL Tier A saves BaBar! • Want to use Grid job submission tools – now • Looking at SRB and RLS Tim Adye

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