David Colling

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Performance of the LHC Computing Grid (LCG)
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Thanks Slides/pictures/text taken from several
people including Les Robertson, Jamie Shears, Bob
Jones, Gabriel Zaquine, Jeremy Coles, Gidon Moont

Caveat LCG means different things to different
people and funding bodies.
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Contents

• Description of the LCG, what the target are, how
  it works.
• The monitoring that is currently in place
• The current and future metrics.
• The Service Challenges
• The testing and release procedure

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The LHC
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What is the LHC?

• LHC will collide beams of protons at an energy of
  14 TeV
• Using the latest super-conducting technologies,
  it will operate at about 270ºC, just above the
  absolute zero of temperature
• With its 27 km circumference, the accelerator
  will be the largest superconducting installation
  in the world.
• Four detectors constructed and operated by
  international collaborations of thousands of
  physicists, egineers and technicians.

The largest terrestrial scientific Endeavour
ever undertaken Due to start taking data in 2007
LHC is due to switch on in 2007 Four
experiments, with detectors as big as
cathedrals ALICE ATLAS CMS LHCb
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Data Volume
Data accumulating at 15 PetaBytes/year Equivalen
t to writing a CD every 2 seconds
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The Role of LCG

• LCG is the system on which this data will be
  analysed and similar volumes of MC simulation
  generated
• High Energy Physics jobs have particular
  characteristics e.g. they are thankfully
  parallel
• However, LCG and EGEE are very closely linked
  and EGEE has a more general remit e.g. biomed,
  earth obs, etc applications as well HEP

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Middleware and Deployment

• Current Middleware based on EDG but hardened
  and extended
• New middleware being developed with the EGEE
  project
• Deployment and monitoring is also done jointly
  with EGEE

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The System (ATLAS Case)
10 Tier-1s reprocess house simulation Group
Analysis
Workstations
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The World as seen by the EDG
Now a happy user
Replica Location service (Replicac Catalogue)
Each Site consists of
edg-job-get-output ltdg-job-idgt
VO server
Confused and unhappy user
So now the user knows about what machines are out
there and can communicate with them however
where to submit the job is too complex a decision
for user alone.
What is needed is an automated system
So lets introduce some grid infrastructure
Security and an information system
This is the world without Grids

• Sites are not identical.
• Different Computers
• Different Storage
• Different Files
• Different Usage Policies

Workload Management System (Resource Broker)
WMS using RC decide on execution location
Logging Bookkeeping
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So what is actually there now?

• Currently, 138 sites in 36 countries
• 14K cpus, 10PB storage
• 1000 registered users (gt100 active users)

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Monitoring LCG/EGEE

• Four forms of monitoring (demos)
• What are the state of a given site
• What is currently in being used
• Accounting how many resources have been used by
  a given Virtual Organisation.
• EGEE quality assurance

These different activities are not always well
connected
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What is the state of site

• Series of site functional tests run
  automatically at every site some involve asking
  a site questions some by running jobs
• These tests are defined as critical or
  non-critical. If a site consistently fails
  critical tests automated messages are sent to the
  site and it will be removed from the information
  system if the error is not connected.
• Also analyses the information published by a
  site.

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What is the state of site
Information gathered at two GOCs http//goc.grid.s
inica.edu.tw/ and http//goc.grid-support.ac.uk/
gridsite/gocmain/
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What is the state of site
Maps as well
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What is currently being usedGridIce
http//gridice2.cnaf.infn.it50080/gridice/site/si
te.php Kind of like the gstat asked for earlier
today
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Accounting APEL
Uses the local batch system logs and publishes
information over RGMA
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Quality assurance
Interrogates the logging and bookkeeping

• Overall Job success, from January 2005
• Job Success rate Done(ok) / (Submitted-Cancelled
  )
• Results should be validated

• http//ccjra2.in2p3.fr/EGEE-JRA2/QAmeasurement/sho
  wstatsVO.php

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Quality assurance

• VOs job throughput and success rate, from January
  until May-2005

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Quality assurance
Next step is to understand these failures
By the end of June will also will measure the
overhead caused by running via the LCG by
measuring the running time/total time
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Quality assurance

• Many other metrics have been suggested (especialy
  in the UK) including
• Number of user ( from different communities)
• Training quality
• Maintenance and reliability (already measured)
• Upgrade time etc etc

UK sites only, target was 3 weeks
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Demos
http//www.hep.ph.ic.ac.uk/e-science/projects/demo
/index.html
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How will we know if we are going get there?

• There are an ongoing set of service challenges
• Each Service Challenge growing in complexity
  approaching the full production service
• Currently we are between SC2 and SC3.
• SC2 only the T0 and T1.
• SC3 will involve 5 T2s as well and SC4 will
  involve all T2 sites.

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Service Challenge 2

• Goal for throughput was gt600MB/s daily average
  for 10 days was achieved - Midday 23rd March to
  Midday 2nd April
• Not without outages, but system showed it could
  recover rate again from outages
• Load reasonable evenly divided over sites (give
  network bandwidth constraints of Tier-1 sites)

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Service Challenge 3 and beyond
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Testing and deployment

• Multi stage release
• New components first tested on the testing
  testbed. Rapid feedback to developers. This
  testing to include performance/scalability
  testing. Currently, this only at 4 (5) site.
  CERN, NIKHEF, RAL, Imperial (two installations)
• Pre-production testbed
• Releases on to production every 3 months

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Conclusions

• Very hard deadline by which this must work
• We are monitoring as much as we can to try to
  understand where our current failures come from.
• We have a release process that hopefully will
  improve performance of future releases

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http//goc.grid-support.ac.uk/gridsite/monitoring/
http//goc.grid.sinica.edu.tw/gstat/ http//gr
idice2.cnaf.infn.it50080/gridice/site/site.php h
ttp//www.hep.ph.ic.ac.uk/e-science/projects/demo/
index.html