Anne C. Elster 1

CLUSTER TECHNOLOGIES

(Foilene ble også presentert på NOTUR 2003)

Anne C. Elster

Dept. of Computer & Information Science (IDI)Norwegian Univ. of Science & Tech. (NTNU)

Trondheim, Norway

NFR 30. juni, 2003

Anne C. Elster 2

Clusters (Networks of PCs/Workstation)

Are they suitable for HPC?

Advantage:Cost-effective hardware since uses

COTS (Commercial Of-The-shelf) parts

BUT: Typically much slower processor interconectes than traditional HPC systems

What about usability?NTNU IDI’s 40-node AMD 1.46GHz cluster2GB RAM, 40GB disk, Fast Ethernet

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Cluster Technologies:NOTUR Emerging Technology project

Collaboration between NTNU & Univ. of Tromsø

Goal: Analyze Cluster technologies’ suitability for HPC

by looking at some of the most interesting NOTUR applications

• The results will provide a foundation for decisions regarding future HPC programs

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Main Collaborators include

• Anne C. Elster (IDI, NTNU) – Project leader• Otto Anshus & Tore Larsen (CS, U of Tromsø• Torbjørn Hallgren (IDI, NTNU)• Einar Rønquist (IMF, NTNU)• Master , Ph.D. Students & Post Docs at NTNU and Univ.

of Tromsø

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General Issues to Consider:

• Why cluster vs. Powerful desktop vs. Large SMPs?

• What are the total costs associated with clusters (harware, software, support, usability)

• 32-bit vs. 64-bit architectures

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Cluster Project ACTIVITIES:

• Profiling & Tuning Selected Applications:

– Physics and Chemistry Codes (Elster & students, Dept. of Computer Science Dept.,

NTNU)

– Profiling & User-Analysis of Amber, Dalton & Gaussian (Tor Johansen & staff, Comp. Center, U of Tromsø)

– Optimization & tool analysis of Dalton (Anshus & PostDoc/student, Dept. of Comp. Sci., U of Tromsø)

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Cluster Project ACTIVITIES continuted:

• Execution Monotoring(Anshus, Tore Larsen & students, CS, U of T)

• Visualization servers, etc.(Hallgren, Elster & students, CS, NTNU)

• Impact of future numerical algorithms(Rønquist & student, Dept. of Mathematics, NTNU

• Interface with NOTUR ET – Grid Project(Elster, Harald Simonsen and colleagues, staff & students associated with the NOTUR ET Cluster & Grid projects)

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Some cluster issues discovered:

• Performance of programs can individually vary on different machines

• FORTRAN problems:– Different FORTRAN implementations have

non-stardard add-ons (e.g. FORTRAN 90)– Leads to great difficulty in porting code to a

different platform with a different Fortran compiler (e.g. by a different vendor)

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Some cluster issues discovered continued:

• Global operations have more severe impact on performance on clusters than traditional supercomputers since communication between processors take relatively more time of total execution time

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The ”Ideal” Cluster -- Hardware

• High-bandwidth network

• Low-latency network

• Low Operating System overhead (tcp causes ”slow start”)

• Great floating-point performance (64-bit?)

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The ”Ideal” Cluster -- Software

• Compiler that is:– Portable– Optimizing

• Do extra work to save communication

• Self tuning /Load ballanced

• Automatically choose best algorithm

• One-sided communication support?

• Optimized middleware

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For more information:

Poster session at NOTUR• Cluster Project stand

- several posters+ smoke simulation demo

• Poster by Torbjørn Vik et. al.• Poster by Lars Ailo Bongo

Email: elster@computer.org