CERN december-00 La Politique du tout PC au CERN Séminaire EDF Clamart – 15 décembre 2000 Les Robertson CERN/IT – Genève

CERN december-00 - #2les robertson - cern/it Sommaire Le problème La stratégie Les difficultés

CERN december-00 Le problème

CERN december-00 - #4les robertson - cern/it Architectures & operating systems supported at end 1999 AIX Windows NT Irix Solaris Digital Unix HP-UX MAC-OS Linux Windows 95 SPARC MIPS Intel IA-32 PA-RISC Power PC Alpha Windows 2000 The legacy of ten years of RISC computing

CERN december-00 - #5les robertson - cern/it 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 ?

LOrganisation Européenne pour la Recherche Nucléaire 20 pays européens 2,700 employées 6,000 utilisateurs CERN

december-00 - #7les robertson - cern/it The Large Hadron Collider - LHC LHC accelerator under construction Proton-proton collider 27 km of super-conducting magnets Target date for first beams Four experiments Example - CMS 2000 physicists, 150 universities

The LHC Detectors CMS ATLAS LHCb 3.5 PetaBytes / year ~10 8 events/year

CERN december-00 - #9les robertson - cern/it 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 ………?

network servers tape servers disk servers application servers Generic computing farm Cern/it/pdp-les.robertson

~10K SI processors Non-LHC Moores Law – estimate of the capacity for fixed level of investment, fixed number of processors LHC 10-20K cpus?

network servers tape servers disk servers application servers Generic computing farm Cern/it/pdp-les.robertson LHC physics facility – 4 experiments 2 M SPECint K processors 2 PByte disk >20 K disks

CERN december-00 - #13les robertson - cern/it 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

CERN december-00 La stratégie

CERN december-00 - #15les robertson - cern/it 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

CERN december-00 - #16les robertson - cern/it 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

CERN december-00 - #17les robertson - cern/it 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 AIX WNT Irix Solaris Digital Unix HP-UX MAC-OS Linux Windows 95 SPARC MIPS Intel IA-32 PA-RISC Power PC Alpha Linux Windows 2000 Intel IA ?

CERN december-00 Les difficultés et l'état de la migration

CERN december-00 - #19les robertson - cern/it 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

CERN december-00 - #20les robertson - cern/it 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 Linux+Intel are as good as any! In the past, the production use of multiple architectures was an important factor in finding bugs

CERN december-00 - #21les robertson - cern/it 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

CERN december-00 - #22les robertson - cern/it 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

CERN december-00 - #23les robertson - cern/it 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