La Politique du tout PC au CERN

1
La Politique du tout PC au CERN
Séminaire EDF Clamart 15 décembre 2000 Les
Robertson CERN/IT Genève
2
Sommaire

• Le problème
• La stratégie
• Les difficultés

3
Le problème
4
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
5

• 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 ?

6
LOrganisation Européenne
pour la Recherche Nucléaire 20 pays
européens 2,700 employées 6,000
utilisateurs
7
The Large Hadron Collider - LHC

• LHC accelerator under construction
• Proton-proton collider
• 27 km of super-conducting magnets
• Target date for first beams - 2005
• Four experiments
• Example - CMS
• 2000 physicists, 150 universities

8
The LHC Detectors
CMS
ATLAS
3.5 PetaBytes / year 108 events/year
LHCb
9
HEP Computing Characteristics

• Large numbers of independent events
• trivial parallelism
• Large data sets
• smallish records
• mostly read-only
• Modest I/O rates
• few MB/sec per fast processor
• Modest floating point requirement
• SPECint performance
• ? High Througput Computing
• Very large aggregate requirements computation,
  data
• Scaling up is not just big it is also complex
• and once you exceed the capabilities of a single
  geographical installation ?

10
Generic computing farm
network servers
application servers
tape servers
les.robertson_at_cern.ch
disk servers
Cern/it/pdp-les.robertson 10-98-10
11
10-20K cpus?
Non-LHC
10K SI951200 processors
LHC
Moores Law estimate of the capacity for fixed
level of investment, fixed number of processors
12
Generic computing farm
network servers
application servers
LHC physics facility 4 experiments 2 M
SPECint95 10-20K processors 2 PByte disk gt20 K
disks
tape servers
les.robertson_at_cern.ch
disk servers
Cern/it/pdp-les.robertson 10-98-12
13
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

14
La stratégie
15
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

16
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

17
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
18
Les difficultés et l'état de la migration
19
Difficulties - I

• Physics (almost) entirely Unix based
• Linux is not quite ready
• (Too) wide a choice of kernels, compilers,
  debuggers
• Different versions supported by different
  applications
• Some applications not supported on Linux
• 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

20
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

21
Current Status Physics

• For older experiments
• Strong resistance to aggressive migration
  proposal
• Agreement for complete freeze on all proprietary
  Unixes during 2003
• For future experiments (not yet collecting data)
  
• General agreement on Linux/Intel for
  production,but require a second (limited)
  development platform for validation
• For new experiments collecting data now
• Easy to calculate the benefits
• Have already completed migration

22
Current Status other applications

• Desktop applications
• Web, Office, .
• Windows 2000
• 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 (Outlook/Netscape)
• Strong pockets of MAC resistance led by the
  Directorate

23
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 trois quarts des
  systèmes installés et 90 de la capacité
  sont Linux/Intel