Transcript RAL Tier A - PPD - STFC Particle Physics Department

BaBar Grid
Tim Adye
Particle Physics Department
Rutherford Appleton Laboratory
PP Grid Team
Coseners House
8th November 2002
8th November 2002
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Talk Plan
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BaBar distributed computing model
RAL Tier A
Remote job submission
BaBar VO and Authorisation
Metadata
Data distribution
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The BaBar Collaboration
9 Countries
8th November 2002
74 Institutions
Tim Adye
566 Physicists
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PEP-II e+e- Ring and BaBar Detector
LER (e+, 3.1 GeV), I(e+ )=2.1 A
Linear Accelerator
HER (e-, 9.0 GeV), I(e- )=1.0 A
BaBar
PEP-II ring: C=2.2 km
BABAR
May 26, 1999: 1st events recorded by BaBar
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
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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
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Remote Job Submission
Short 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” JDL Requirements; 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.
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Remote Job Submission
Medium 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
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BaBar VO and Authorisation
• Use certificates from EDG and ESnet CAs 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
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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
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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
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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
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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
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