La Politique du tout PC au CERN

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La Politique du tout PC au CERN
CUIC Arcachon 21-22 juin 2000 Les
Robertson CERN/IT Genève
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Sommaire

• Le problème
• La stratégie
• Les difficultés

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Le problème
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Architectures operating systems supported at
end 1999
Digital Unix
SPARC
Solaris
MIPS
AIX
The legacy of ten years of RISC computing
Alpha
Windows 2000
Irix
Windows 95
Windows NT
Linux
Power PC
MAC-OS
Intel IA-32
PA-RISC
HP-UX
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• Combien darchitectures et systèmes
  dexploitation sont vraiment nécessaire?
• Combien coûte le support?
• Combien vaut la diversité?
• Comment imposer des limitations de choix dans un
  environnement de recherche scientifique ?

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CERN - The European Organisation for Nuclear
ResearchThe European Laboratory for Particle
Physics

• Fundamental research in particle physics
• Financed by 20 European countries
• 6,000 users (researchers) from all over the world
• LHC accelerator under construction
• Proton-proton collider
• 27 km of super-conducting magnets
• Target date for first beams - 2005
• Four experiments
• 2000 physicists, 150 universities

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CMS detector - as big as a 6-storey
office block, - costing FF 2.000M - 1 PetaByte
of filtered data per year
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The LHC Detectors
CMS
ATLAS
3.5 PetaBytes / year 108 events/year
LHCb
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Performance or Throughput?

• High Throughput Computing
• mass of modest problems
• throughput rather than performance
• resilience rather than ultimate reliability
• Ten years of experience in exploiting
  inexpensive mass market components
• But we need to marry these with inexpensive
  highly scalable management tools
• Much in common with data mining, Internet
  computing facilities,

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10-20K cpus?
Non-LHC
10K SI951200 processors
LHC
technology-price curve (40 annual price
improvement)
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Non-LHC
LHC
technology-price curve (40 annual price
improvement)
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lmr for Monarc study- april 1999
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LHC physics facility 4 experiments 2 M
SPECint95 10-20K processors 2 PByte disk gt20 K
disks
lmr for Monarc study- april 1999
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Summary of the problem

• HEP is using far too many operating systems
• in many cases with only slightly different
  functionality or hardware cost benefits
• and at a high cost for users and support teams
• The scale of LHC computing -
• massive numbers of processors/boxes
• integration of regional computing centres and
  CERN
• ? problem is how to manage on this scale
  while limiting costs of equipment, management
  support
• We must reduce the diversity
• while retaining flexibility
• to use low-cost, mass market components
• and adapt rapidly to changing physics needs

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La stratégie
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Opportunity

• PCs Linux Windows offer an historic
  opportunity to reduce the solution set
• Costs and performance
• PCs will consistently be among the very best
  price/performers for HEP codes
• They may not be the fastest,but they are fast
  enough
• Linux -a non-proprietary operating system
  compatible with the recent Unix history
• Windows a mass market alternative widely used
  on the desktop

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Policy

• Restrict ourselves to PC hardware with Linux
  or Windows 2000
• Develop a migration plan -
• progressively freeze support for other
  Unixes,announcing end-dates which are
  reasonable for old experiments,
• strongly discourage further investments in RISC
  systems by current and future experiments
• install large Linux public facility, testbed for
  future experiments
• Concentrate investment in Linux and Windows
• bring support up to the standards of proprietary
  Unixes
• tackle the problems of scaling the management and
  performance of physics farms and desktops
• seek HEP-wide consensus

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But do not be unrealistic ----

• This is a convergence policy
• which looks realistic now
• and will provide a single starting point for LHC
  computing
• but we can be sure that the industry will not
  stand still, and we shall sooner or later have to
  expand the systems and architectures supported

Digital Unix
SPARC
AIX
MAC-OS
WNT
Solaris
Alpha
Linux
Irix
Intel IA-32
Intel IA-64
- - - ?
Windows 2000
MIPS
Power PC
Windows 95
Linux
HP-UX
PA-RISC
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Les difficultés et l'état de la migration
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Difficulties - I

• Physics (almost) entirely Unix based
• Linux is not quite ready
• (Too) wide a choice of kernels, compilers
• Poor debugging
• Different versions supported by different
  applications
• Complex packages (Oracle, AFS) better go with
  the standard platform
• Stability problems under load
• Who provides in-depth, on-site Linux systems
  support?
• Solution
• Standard Linux Package certified for all CERN
  applications
• Solaris/SPARC for special purposes
• Open posts for Linux experts

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Difficulties - II

• In a research environment
• Easy to estimate the costs of systems support
• Hard to estimate the cost of application
  migration
• The application experts have already moved on
• The developers have other (more interesting)
  problems to solve
• The problem is not only to port the code
• but (more important) to acquire confidence in the
  physics results
• Compiler, architecture, old bugs
• But there are signs that LinuxIntel are as good
  as any!
• In the past, the production use of multiple
  architectures was an important factor in finding
  bugs

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Current Status Physics

• For older experiments
• Strong resistance to aggressive migration
  proposal
• Now aiming at complete freeze on all proprietary
  Unixes during 2003
• For future experiments (not yet collecting data)
  
• General agreement, but reserve position on
  alternative platform for validation
• For new experiments collecting data now
• Easy to calculate the benefits
• Have already completed migration

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Current Status other applications

• Engineering applications
• Aggressive migration plan to Windows NT/2000
  Linux, with some residual SUN
• Major exception is mechanical CAE (Euclid
  Digital Unix)
• Administration
• Database (Oracle) on SUN
• Clients Web-based (Netscape)
• Strong pockets of MAC resistance led by the
  Directorate

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Conclusions

• Les besoins énormes du LHC exigent la
  standardisation et lutilisation des composants
  bon-marché
• Opportunité Linux Windows 2000 avec Intel
  IA32/64 Ethernet
• Grande inertie (résistance?) de la part des
   vielles expériences - il faudra 4 années
  pour terminer la migration
• Mais déjà plus de la moitié des systèmes
  installés et 75 de la capacité sont
  Linux/Intel