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Performance issue when job exclusivity not selected

    Question

  • Hello,

    I'm facing a strange behavior on a HPC compute cluster based on Windows HPC 2012 R2. When starting a 32 cores ANSYS Fluent job from Fluent Launcher, performances are poor (~50s to compute a 10 iterations time step). Server used are 12 (2x6) cores servers with IB.

    If I modify the same job and activate the job option "use assigned resources exclusively for this job", performances are normal (~8s per time step).

    If I start the same job in batch mode performances are normal (~8s per time step), whether the option "use assigned resources exclusively for this job" is activated or not.

    Of course, there were no other jobs on the Compute Cluster when I ran these tests. I did the same tests with SCCM+ and did not notice any performances issue with the same servers. ANSYS support claims it's an MS HPC issue as the job runs normally when exclusivity is activated.

    Does anyone have an idea of what is happening or any lead I could follow ? I already spend few days on this without success.

    Thank you

    Sebastien

    Friday, December 02, 2016 9:09 AM