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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

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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

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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

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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

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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, …)

Priorities and next steps