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Massimo Lamanna CERN IT

Input for a discussion on the LHC heavy-ion run (2010) update of the presentation to the 21-SEP-2010 LHCC referees’ meeting. Massimo Lamanna CERN IT. Checking the rates (RAW). The following figures correspond to 100% duty cycle (LHC*Experiment)

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Massimo Lamanna CERN IT

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  1. Input for a discussion on the LHC heavy-ion run (2010)update of the presentation to the 21-SEP-2010 LHCC referees’ meeting Massimo Lamanna CERN IT

  2. Checking the rates (RAW) • The following figures correspond to 100% duty cycle (LHC*Experiment) • One can then fold them with something of the order of the pp LHC duty cycle • All RAW are recorded to tape at CERN • ALICE • 12.5 MB/evt * 200 Hz (2,500 MB/s) • 200 TB/day • ATLAS • 2.2 MB/evt * 50-100 Hz (110-220 MB/s) • 10-20 TB/day • CMS • 12 MB/evt * 150 Hz (1,800 MB/s) • NB: large event size due to no zero suppression for HI 2010 • 150 TB/day • LHCb • No HI data taking

  3. Checking the rates (processing and export) • ALICE • No complete export/processing during the heavy-ion run • Export to completed in the weeks after HI (before 2011 pp) • During the HI run: • ~10-20% of the RAW rate (hence ~100MB/s) • ~10-20% RAW reconstruction (but NO ESD recording) • ATLAS • Complete RAW export to 1 sites (1 copy across ATLAS T1s) • Some processing: some ESD+DESD(+AOD) to tape and export • NB: (ESD+DESD)/RAW is ~ 6 (Very large ESD and DESD) • Assumption: at CERN express stream only – the rest is done at the Tier1s • Note: no ESD+DESD flux “back to CERN” (potentially very high) • CMS • No complete export during the heavy-ion run • Software zero-suppressed data will be shipped abroad after the run (1 site) • Full processing at CERN • RECO/RAW is 1/6 • RECO export to a few sites

  4. General considerations and constraints • These figures clearly exceed the foreseen data rates • CASTOR has some headroom (resilience, catch up, etc...) • Needed to achieved sustained and sustainable operations • “Background activities” like users analysis cannot be stopped • In addition we had ever no readiness test for combined HI operations • 4 experiments in pp mode and ALICE in heavy-ion mode alone • Strategy • Collecting these figures to prepare at best for heavy-ion operations • Trying to cope with the higher needs from the experiments • Get priorities among different activities

  5. Priorities and next steps • Priorities • Within each experiment • RAW to tape (data integrity) • RAW export (data integrity) • Processing (quality control and physics) • Export of processed data (physics and data quality control) • Interplay with “background activities” (pp analysis!, ...) • Across the experiments • Expect a statement from the referees • Iterate with the experiments • Use of 2011 resources to increase data rates • Uncharted area (scaling properties of the system depends on the actual workflows features (file sizes/rate, rate on CASTOR central services, …) • Combined test (ALICE+CMS) being scheduled • Priorities are needed to implement fallback plans • And collaboration from the experiments to control the load (user activity, reprocessing, …)

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