Site Support Team - Documentation
Introduction to CMS Computing Operations

The purpose of this twiki is to provide a General Overview of the work done by the Computing Operations Team for CMS and to be used while training new members.

Processing LHC Data

The LHC produces 600 million collisions every second in each detector, which generates approximately one petabyte of data per second. None of today’s computing systems are capable of recording such rates. Hence sophisticated selection systems are used for a first fast electronic pre-selection, only passing one out of 10 000 events. Tens of thousands of processor cores then select 1% of the remaining events. Even after such a drastic data reduction, the four big experiments, ALICE, ATLAS, CMS and LHCb, together need to store over 25 petabytes per year. The LHC data are aggregated in the CERN Data Centre, where initial data reconstruction is performed, and a copy is archived to long-term tape storage. Another copy is sent to several large scale data centres around the world. Subsequently hundreds of thousands of computers from around the world come into action: harnessed in a distributed computing service, they form the Worldwide LHC Computing Grid (WLCG), which provides the resources to store, distribute, and process the LHC data. WLCG combines the power of more than 170 collaborating centres in 36 countries around the world, which are linked to CERN. Every day WLCG processes more than 1.5 million ‘jobs’, corresponding to a single computer running for more than 600 years.

• Movie: http://cds.cern.ch/video/CERN-MOVIE-2013-041-001
• Produced by: CERN IT department
  Director: The Little Big Studio
  00:05:09:16 / 15 April 2013 /

Plans from the LHC - 2015

• Information about:
  • Distributed Computing model
  • Future improvements
  • Goals
  • https://dl.dropboxusercontent.com/u/2077046/CMS/CompOps/130515_Fisk_Plans_WLCG.pdf

Production Flowchart

The Glidein-based Workflow Management System (based on Condor)

• Introduction and General Info:
  • http://www.uscms.org/SoftwareComputing/Grid/WMS/glideinWMS/doc.prd/index.html

• How does it work?

• More info:
  • https://twiki.cern.ch/twiki/bin/view/CMSPublic/GlideinWMSMonitoring

Site Support Team - Overview

• An introduction to the Site Support Team:
  • 130509_-_SiSuTeam_Overview.pdf