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DELPHI experience. I left collaboration in 1997 so I won’t talk about data preservation but another costly effort Change of offline compute platform from IBM mainframe  RISC UNIX

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delphi experience
DELPHI experience
  • I left collaboration in 1997 so I won’t talk about data preservation but another costly effort
    • Change of offline compute platform from IBM mainframe  RISC UNIX
  • Caveat: this recollection covers a period 20 years ago and is reconstructed from my own notes and mails from that period. Any error is entirely mine…
compute platform
Compute platform
  • Up to ~1992 main computing platform @CERN was the IBM mainframe CERNVM
  • As a physicist one quickly learned about
    • VM/CMS, REXX, XEDIT
  • DAQ and production learned VAX VMS
    • All offline code cross-compiled and certified
      • YPATCHY with CARds and CRAdles to control the versioning and platform differences
      • DELPHI’s own farms in p8 and basement of bat27 was entirely VAX based, at least to begin with
    • But for normal physics analysis there were never enough VAX compute resources to motivate a serious take-up
delphi offline in numbers
DELPHI offline in numbers
  • 16 sub-detectors
  • ~1Hz trigger rate, average event size 50kB, peak event size 200kB (1990)
  • Yearly total DST (Data Summary Tape) volume
    • 1989: 3x IBM 3480 cartridge
    • 1990: 38x
    • 1991: 146x
  • Source code was pretty FORTRAN 77 formatted for punch-card compatibility
  • Main packages
  • DELSIM: 0.5-1M of SLOC (DELPHI didn’t use Geant3)
  • DELANA: ~>1M SLOC
migrate to risc unix
Migrate to RISC/UNIX
  • Compute cycles on CERNVM were precious
  • If you wanted run >1hrs job
    • go to offline computing office and give your justification
    • Priority was given to:
      • Higgs search and Z0 resonance precision measurements
    • QCD studies (like mine) were queued behind

 Strong motivation to seek for other resources

benchmark that convinced me
Benchmark that convinced me

2x60 = 120 CPUs/event

2x38x24x60x60/55’000

119 CPUs/event

moving to risc unix
Moving to RISC/UNIX
  • Core teams (~1993):
    • DELPHI
      • Alfonso Lopez-Fernandez (CERN) (later Gilbert Grosdidier)
      • D. M. Edsall (Iowa State University Ames HEP Group)
      • Luiz Mundim(LAFEX-CBPF/PUC)
      • O. Bärring (CERN)
    • CN (IT) SHIFT
      • Frédéric Hemmer
      • Christian Boissat
    • CN Public Login (+AFS): Tony Cass
  • Tasks
    • Create an attractive and reliable compute and storage resource
      • More for less ($/IBM cycle  $/Risc cycle)
    • Cross-compile and certify
    • Mirror production and analysis software repos
      • Nightly builds + tests
    • Facilitate migration (REXX sh, csh)
    • Write targeted user guides (UNIX, SHIFT, FATMEN, …)
    • User support, public presentations and publicity
  • Rough cost:
    • Hardware (provided by CN): negligible (probably ~10-2 x IBM)
    • People: DELPHI ~6 person years for the full migration
  • Dedicated efforts completed in ~1995-6. Daily tasks (support etc.) integrated with general offline activities
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