The ATLAS Computing & Analysis Model Roger Jones Lancaster University ATLAS UK 06 IPPP, 20/9/2006

RWL Jones 13 Sept 2006 Geneva 2 ATLAS Facilities (Steady State) Tier 0 Center at CERNTier 0 Center at CERN Raw data  Mass storage at CERN and to Tier 1 centers Swift production of Event Summary Data (ESD) and Analysis Object Data (AOD) Ship ESD, AOD to Tier 1 centers  Mass storage at CERN Tier 1 Centers distributed worldwide (10 centers)Tier 1 Centers distributed worldwide (10 centers) Re-reconstruction of raw data, producing new ESD, AOD (~2 months after arrival and at year end) Scheduled, group access to full ESD and AOD Tier 2 Centers distributed worldwide (approximately 30 centers)Tier 2 Centers distributed worldwide (approximately 30 centers) On demand user physics analysis of shared datasets Monte Carlo Simulation, producing ESD, AOD, ESD, AOD  Tier 1 centers CERN Analysis FacilityCERN Analysis Facility Heightened access to ESD and RAW/calibration data on demand Calibration, detector optimization, some analysis - vital in early stages Tier 3 Centers distributed worldwideTier 3 Centers distributed worldwide Physics analysis

RWL Jones 13 Sept 2006 Geneva 3 New Straw Man Profile yearenergyluminosityphysics beam time GeV 5x10 30 protons - 26 days at 30% overall efficiency  0.7*10 6 seconds TeV 0.5x10 33 protons - starting beginning July 4*10 6 seconds ions - end of run - 5 days at 50% overall efficiency  0.2*10 6 seconds TeV 1x10 33 protons:50% better than 2008  6*10 6 seconds ions: 20 days of beam at 50% efficiency  10 6 seconds TeV 1x10 34 TDR targets: protons:  10 7 seconds ions:  2* 10 6 seconds

RWL Jones 13 Sept 2006 Geneva 4 Evolution

5 Observations The T2s tend to have too high a cpu/disk ratioThe T2s tend to have too high a cpu/disk ratio Optimal use of the T2 resources delivers lots of simulation with network and T1 disk consequences (although the higher cpu/event will reduce this) The T2 disk only allows about ~60% of the required analysis Other models would seriously increase network traffic GridPP planned disk/cpu balanace is right of courseGridPP planned disk/cpu balanace is right of course But not the current values And plans are plans until funded! Simulation time is crippling - need a real asessment of what is *need*Simulation time is crippling - need a real asessment of what is *need* Bigger ESD means few ESD events accessedBigger ESD means few ESD events accessed

RWL Jones 13 Sept 2006 Geneva 6 Streaming This is an optimisation issueThis is an optimisation issue All discussions are about optimisation of data access TDR had 4 streams from event filterTDR had 4 streams from event filter Primary physics, calibration, express, problem events Calibration stream has split at least once since! Now envisage ~10 streams of RAW, ESD, AODNow envisage ~10 streams of RAW, ESD, AOD Based on trigger bits (immutable) Optimizes access for detector optimisation Straw man streaming schemes to be tested in large-scale exercises Debates between inclusive and exclusive streams (access vs data management) - inclusive may add ~10% to data volumesDebates between inclusive and exclusive streams (access vs data management) - inclusive may add ~10% to data volumes (Some of) All streams to all Tier 1s(Some of) All streams to all Tier 1s Raw to archive blocked by stream and time for efficient reprocessing

RWL Jones 13 Sept 2006 Geneva 7 TAG in Tiers File-based TAGs allow you to access events withing files directlyFile-based TAGs allow you to access events withing files directly Full relational database TAG for selections over large datasetsFull relational database TAG for selections over large datasets Full relational database too demanding for most Tier 2s Expect Tier 2 to hold file-based tag for every local dataset Supports event access and limited dataset definition Tier 1 will be expected to hold full database TAG as well as file formats (for distribution) Tentative plans for queued access to full database version

RWL Jones 13 Sept 2006 Geneva 8 Getting Going Every group should have a Grid User InterfaceEvery group should have a Grid User Interface Ideally one on every desktop This was presented about a year ago to HEP SYSMAN But many groups do not seem to have one Pressure needed from the grass roots?Pressure needed from the grass roots? Users needUsers need A Grid certificate Join the ATLAS Virtual Organisation

RWL Jones 13 Sept 2006 Geneva 9 Analysis Resources In terms of non-local UK resources, we are already in the Grid EraIn terms of non-local UK resources, we are already in the Grid Era UK resources are asked for centrally via GridPP These are dominated by production tasks for ATLAS Some additional capacity for analysis and group activity All of this is Grid based - no nfs disk, no local submission If UK groups have identified needs that are not in the ATLAS central planning, please justify it and send it to me We need to know >3 months in advance Quota and fair-share technologies are being rolled-out, but at present people must be responsible This is not an infinite resource Using large amounts of storage can block the production

RWL Jones 13 Sept 2006 Geneva 10 Computing System Commissioning This is a staged series of computing exercisesThis is a staged series of computing exercises Analysis is a vital componentAnalysis is a vital component Need people doing realistic analysis by the Spring If we don’t get the bugs found then, physics will suffer Interesting events mixed with background Data dispersed across sites

RWL Jones 13 Sept 2006 Geneva 11 Conclusions Computing Model Data well evolved for placing Raw, ESD and AOD at Tiered centersComputing Model Data well evolved for placing Raw, ESD and AOD at Tiered centers Still need to understand all the implications of Physics Analysis Distributed Analysis and Analysis Model Progressing well But at present, data access is not fit for purpose (action underway) A large ESD blows-up the model CPU/Disk imbalances really distort the model The large simulation time per event is crippling in the long term SC4/Computing System Commissioning in 2006 is vital.SC4/Computing System Commissioning in 2006 is vital. Some issues will only be resolved with real data in Some issues will only be resolved with real data in