LHCb usage of Tier2s

PhC 2

LHCb Computing Model

m Guidelineso Evaluate computing needs for all activities

P SimulationP Real data processingP Analysis

o Map it to expected resources at Tier0, Tier1s (6) and Tier2s (including non MoU)

o Large needs for simulation (precision experiment)P Use full power of Tier2s (and others) for simulation

o Minimize potential file access problemsP For processing and analysis

m TDR baselineo Run processing applications at Tier0/CAF and Tier1s

P For reprocessing, largely use also the Online HLT farmd Estimated ~50% of needs, but needs developments

o Run simulation primarily at Tier2s P Use any opportunistic site

LHCb

PhC 3

LHCb Analysis

m Batch analysiso Using Grid facilities at Tier0 and Tier1s

P All stripped DSTs available at all sitesP MC DSTs at 3 sites (CERN + 2)

o Storage of output (microDST, Ntuple…) on Grid SEP TxD1 storage (LHCb_USER token)

o Expected number of selected events is small (<107 <~1 TB)

m End user analysiso Well feasible on desktop / laptopo Assume Tier3/4: not part of Grid activities

P Under institute responsibility to set up:d Storage and dataset replicationd Software installation

P Develop multi-core/processor interactive programming (GaudiParallel, in collaboration with LCG-AA/PH-SFT)

LHCb

PhC 4

LHCb Analysis on Tier2 ?

m First goal is to get it running reliably on Tier1so Experience a lot of file access problems

P Only 2 flavors (Castor and dCache)P Full time job to follow up on 7 sitesP No central manpower for supporting more sites / flavors

m How could a Tier2 be used for analysis?o Grid resources are shared

P LHCb does not want to support “national computing”o Our CPU requests are balanced between Tier1 and

Tier2P Therefore analysis should come from additional

resourceso Local LHCb group(s) should be involved in the

supportP Dataset assignmentP Problem resolution (data access, software installation…)

m Proposalo Investigate feasibility with a few selected sites (1-2)o Define a model that doesn’t increase the load on

central supportLHCb