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The story of BaBar: an IT perspective

The story of BaBar: an IT perspective. Roger Barlow DESY 4 th September 2002. OPAL. BaBar (Work in progress). Example:      -    0   . History. Datataking: “Drinking from a firehose”. 4.2 ns. 32 SUN U5. L1 Trigger. L3 Trigger. 1-2kHz. 200+ CPUs. OPR farm.

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The story of BaBar: an IT perspective

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  1. The story of BaBar: an IT perspective Roger Barlow DESY 4th September 2002

  2. OPAL BaBar (Work in progress) Example:  -  0 BaBar: an IT perspective

  3. History BaBar: an IT perspective

  4. Datataking:“Drinking from a firehose” 4.2 ns 32 SUN U5 L1 Trigger L3 Trigger 1-2kHz 200+ CPUs OPR farm PowerPCs in VME crates Data store 30-100 Hz 200 kB/evt BaBar: an IT perspective

  5. Decision taken: approved languages C++ and F90 (Nobody used F90) HEP escapes at last from FORTRAN! Other experiments follow Software immediately becomes VERY object-oriented C++ “Unorthodox but very nice introduction to programming” Amazon.com review BaBar: an IT perspective

  6. Design Old New C++ in practice Abstract objects EmcCluster:AbsRecoCalo AbsRecoCalo: AbsEvtObj EmcClusterMoments: EmcAbsClusterProperty EmcClusterDistance: EmcAbsClusterProperty The software was written on time and it worked. BaBar: an IT perspective

  7. RogueWave Commercial class library Built in to software from start Superseded by STL, CLHEP Licence arrangements restrictive/expensive Now (painfully) removed Calibration System impressive technically Can’t do what you want it to Some lessons Event Display Powerful system (‘Event display server’) written by experts Unwieldy and unreliable for non-experts away from SLAC Little used BaBar: an IT perspective

  8. ‘Persistent data’ Objects still present when a job is run again- stored on disc Need to handle pointers Need to match data on disk to objects the program knows about Need to do this fast and furiously Objectivity does this – no alternative Performance issues in OPR: solved (hard work+vendor co-operation) Performance issues in analysis: not satisfactory (physicists more random) KANGA Long-term viability? Objectivity BaBar: an IT perspective

  9. Success: the penalty PEPII delivers and BaBar can handle it Design Luminosity 3 1033 achieved Now 5 1033 Heading for 4 1034 BaBar efficiency ~ 95% (This is a race. KEK and Belle are close behind!) • Data handling • Need to provide • Disk (or tape) for data storage • Machines for OPR • Machines for analysis • Moore’s Law is not strong enough • Need new computing model • Central  Distributed BaBar: an IT perspective

  10. File Transfer Data transfer From SLAC to outside sites Large (RAL, IN2P3) and small (university) Use network transfer rather than shipping tapes ESNET in US, JANET+ GEANT in Europe Use RAL, Rome, etc as staging posts File copy programs bbcp and bbftp developed, now standard Copy with multiple streams Achieve 80-100 Mbit/s Data available within days Chasing improvement continuous task BaBar: an IT perspective

  11. Spreading the load Serious computing power at outside institutes Each UK BaBar group ~1TB fast disc (1998) Compute farm (80 CPU) (2000) Used for analysis Used for MC simulation BaBar: an IT perspective

  12. RAL Tier A Centre Similar centres at IN2P3, Bologna, plus Karlsruhe in future UK GRID Funds available Tier 1/A centre at RAL 200+ CPUs 35 TB disk this year (increasing as price drops) Rebate on common fund contribution Everybody happy BaBar: an IT perspective

  13. Future Development Many users running jobs on distributed data with distributed CPUs Don’t want technical detail GRID provides the answer User specifies data description and job Grid tools locate files, find CPUs, submit jobs BaBar today: LHC tomorrow MC:RB BaBar: an IT perspective

  14. Authentication Certificate Authorities Certificates issued by trusted organisations to people they know and trust (or people they trust know and trust) Establish mutual trust within BaBar for UKHEP,CNRS, etc But authentication is not authorisation! Grid Certificate Uses RSA encryption to prove to other computers (‘gatekeepers’) that you are who you say you are BaBar: an IT perspective

  15. Authorisation SLAC MANCHESTER BaBarGrid sites Users with Grid certificates authorised to use resources at all BaBarGrid sites Getting on this list is made easy (for BaBar users with a Grid certificate) Dynamic account pool avoids need for 500x50 userids gridmap files Grid Certificate BaBar VO list cron job cron job BaBar: an IT perspective

  16. The BaBar VO BaBar: an IT perspective

  17. The BaBar Grid Demonstrator Rudimentary Grid submission and retrieval Full features to be added later BaBar: an IT perspective

  18. The Future: Some Possibilities Join EDG testbed rollout More Compute and Storage farms Desk-to-desk Video conferencing Extend VO system for authorisation SRB as universal file system Metadata specification using xml Framework VI BaBar: an IT perspective

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