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Grid computing for CMS. Alain Romeyer (Mons - Belgium). What is the Grid ? Let’s start with an analogy How it works ? (Some basic ideas) Grid for LHC and CMS computing model Conclusion. What is the Grid ?. an integrated advanced cyber infrastructure that delivers: Computing capacity

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Grid computing for CMS

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Grid computing for cms

Grid computing for CMS

Alain Romeyer (Mons - Belgium)

  • What is the Grid ?

  • Let’s start with an analogy

  • How it works ? (Some basic ideas)

  • Grid for LHC and CMS computing model

  • Conclusion

Alain Romeyer - Dec. 2004

What is the grid

What is the Grid ?

  • an integrated advanced cyber infrastructure that delivers:

    Computing capacity

    Data capacity

    Communication capacity

  • Coordinated resource sharing and problem solving in dynamic

  • no centralized control

  • Use standard and open protocols and interfaces

  • deliver nontrivial qualities of service

  • What is not a Grid?

    • A cluster, a network attached storage device, a scientific instrument, a network, etc.

    • Each may be an important component of a Grid, but by itself does not constitute a Grid

For us : A new way of doing science !!!

Alain Romeyer - Dec. 2004

An analogy power electricity on demand access

An analogy : Power electricity (on demand access)

Quality, economies of scale


Alain Romeyer - Dec. 2004

By analogy

By analogy

  • Decouple production and consumption

    • Enable on-demand access

    • Achieve economies of scale

    • Enhance consumer flexibility

    • Enable new device

  • On a variety of scales

    • Department

    • Campus

    • Enterprise

    • Internet

Alain Romeyer - Dec. 2004

Not a perfect analogy

Not a perfect analogy…

  • I import electricity but must export data

  • “Computing” is not interchangeable but highly heterogeneous

    • Computers, data, sensors, services, …

  • So the story is more complicated

  • But more significantly, the sum can be greater than the parts

    • Dynamic allocation of resources

    • Access to distributed services

    • Virtualization & distributed service management

Alain Romeyer - Dec. 2004

How it works grid responsibilities

How it works ? Grid responsibilities

  • Security Infrastructure

    • Authentication (identity)

    • authorization (rights)

  • Management :

    • Information Management

      • Soft-state, registration, discovery, selection, monitoring

    • Resource Management

      • Remote service invocation, reservation, allocation

      • Resource specification

    • Data Management

      • High-performance, remote data access

      • Cataloguing, replication, staging

Alain Romeyer - Dec. 2004

How it works security authentification

How it works ? Security - Authentification

  • Grid Security Infrastructure (GSI)

    • Public key infrastructure (asymmetric)

  • Need to be associated to a Virtual Organisation (VO)

  • Need certificate delivered by a Certification Authority (CA)

    • A certificate (x509 international standard) is :

    • It contains :

      • A subject name (identify the user/person)

      • A user public key

      • The identity of the CA

      • The digital signature of the CA

a digitally signed document attesting to the binding of a public key to an individual entity

Alain Romeyer - Dec. 2004

Grid computing for cms





Cert signing





Digital Signature

How it works ? Security - Authentication


Message Digest


Alain Romeyer - Dec. 2004

Grid computing for cms

Global Manager


Computing Element




Where ?



  • Best actions to satisfy the request :

  • match-making

  • where submit

  • Grid status

  • Decision

Job submission

Status ?

Data Transfert

Publish characs,status, available services…

Storage Element

Job controlCONDOR-G



How it works ? Management

End of job :outputs are stored in your « sand box » ask to download them

Alain Romeyer - Dec. 2004

Some grid e science projects

Some Grid e-science projects

Sloan Digital Sky Survey







Alain Romeyer - Dec. 2004

Egee www eu egee org


  • Enabling Grid for E-science in Europe (2 years project)

  • Funded by the EU, 3 core areas :

    • 1) build a consistent, robust and secure Grid network that will attract additional computing resources.

    • 2) continuously improve and maintain the middleware in order to deliver a reliable service to users.

    • 3) attract new users from industry as well as science and ensure they receive the high standard of training and support they need.

  • Two pilot application selected :

    • Biomedical Grids (bioinformatics and healthcare data)

    • Large Hadron Collider Computing Grid (LCG)

Alain Romeyer - Dec. 2004

Lhc computing grid lcg

LHC Computing Grid (LCG)

Phase I (2002 - 2005) : development phase + series of computing data challenges

Phase II (2006 – 2008) : real production and deployment phase

2 phase


  • LCG goal : prepare the computing infrastructure for the simulation, processing and analysis of LHC data for the 4 experiments.

  • 6 000 physicist working together

  • 12-14 PetaBytes of data will be generated each year (20 millions CDs == 20 km)

  • Analysing this will require the equivalent of 70,000 of today's fastest PC processors(~192 years)

Alain Romeyer - Dec. 2004

Lcg status

LCG status


Total Sites : 82

Total CPUs : 7269Total Storage : 6558 (TB)

Alain Romeyer - Dec. 2004

Cms data production at lhc

CMS data production at LHC

Level 1 Trigger

75 KHz (50 GB/sec)

High Level Trigger

100 Hz (100 MB/sec)

Cluster for the Trigger

~ 1000 – 2000 PCs

Data Recording &

Offline Analysis


1 bunch crossing

Every 25 ns


40 MHz (40 TB/sec)

Alain Romeyer - Dec. 2004

Cms computing model

CMS computing model

Tier 1

~2.5-10 Gbps

FNAL Center

IN2P3 Center

INFN Center

RAL Center

Tier2 Center

Tier2 Center

Tier2 Center

Tier2 Center

Tier2 Center

Tier 2

~2.5-10 Gbps

Tier 3





Physicists work on analysis “channels”.

data for these channels should be cached by the institute server

Physics data cache

0.1 to 10 Gbps


Tier 4


100 MBytes/sec

Online System


CERN Center PBs of Disk; Tape Robot

Tier 0

2.5-10 Gbps

Alain Romeyer - Dec. 2004

Dc04 data challenge

DC04 Data Challenge














  • T1 centres in DC04

  • Pull data from T0 to T1 and store

  • Make data available to PRS

  • Demonstrate quasi-realtime “fake” analysis






March-April 2004

  • T0 at CERN in DC04

  • 25 Hz input event rate

  • Reconstruct quasi-realtime

  • Events filtered into streams

  • Distribute data to T1’s


Alain Romeyer - Dec. 2004

Dc04 processing rate

DC04 Processing Rate

T0 events processed vs. days

T0 event processing rate (Hz)

  • Got above 25Hz on many short occasions

  • Only one full day >25Hz with full system

  • Processed about 30M events

  • DC04 demonstrated that the system can work…at least for well controlled data flow / analysis, and for a few expert users

Next challenge: make it useable by average physicists…and demonstrate that the performance scales acceptably

Alain Romeyer - Dec. 2004



  • Grid becomes a reality

  • Management is the crucial issue that is not fully implemented

    • will be done by the EGEE project

  • For the HEP, LCG II already available and working

  • CMS DC04 has showed that the system starts to work

  • Next data challenge will be crucial :

    • Usable by standard physicist

    • Performances reasonable for LHC

Alain Romeyer - Dec. 2004



  • Belgrid project ( « a Belgian Grid initiative «

    • Regroups academic, public and private partners

    • Goal : share the local computing resources using Grid technologies

    • Status : GridFTP between sites is working

    • Plan : distributed computing

  • BEgrid (belnet) : grid computing for the Belgian Research

    • Belnet : official CA -> certificate also valid for use in EGEE

    • 5 universities connected (KULeuven, UA, UG, ULB and VUB)

    • LCG II and follow the EGEE middleware

Alain Romeyer - Dec. 2004

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