Automation

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  • 1.  cpu ratio

    Posted Sep 18, 2020 06:39 AM

    Hi , .

    hope everybody is well

    I am calculating cpu ratio in my cluster and use this :

    (Get-cluster -name MyCluster  | Get-vm | Where Powerstate -eq “PoweredOn” | Measure NumCpu -sum).sum  /  (((Get-cluster -name MyCluster  | Get-vmhost).extensiondata.summary.hardware | Measure -Property numCpuCores -Sum).sum)

    but I am not sure should second part of command multiply with 2  because hyper-threading is enabled,  because hyper-threading only increase performance by 30% , don actually increase number of CPUs



  • 2.  RE: cpu ratio

    Broadcom Employee
    Posted Sep 18, 2020 07:50 AM

    Moderator: Thread moved to the PowerCLI area.



  • 3.  RE: cpu ratio

    Posted Sep 18, 2020 08:11 AM

    It is a matter of preference.
    Most ratios I calculate use in fact the NumCpuThreads property in the Hardware object.
    That means that HT is taken into account.

    I often provide both, 'CPU Ratio', where I use NumCpuCores, and 'HT Ratio', where I use NumCpuThreads.

    But remember that rules of thumb based on ratios are not absolute.
    As always, it depends.

    Measure what your VM is actually doing (CPU Ready is a good indicator), try to find variations over time, and many more aspects.



  • 4.  RE: cpu ratio

    Posted Sep 18, 2020 08:38 AM

    if calculating CPU radio I use NumCpuThreads the result is 6:1 and I need to add more power to the cluster, but if I use NumCpuThreads then is 3:1 them there is no need for expansion. that is what is confusing me



  • 5.  RE: cpu ratio

    Posted Sep 18, 2020 10:16 AM

    I find a script to calculate CPU ready in cluster , and get value of 31% is that good or bad. I know for vm cpu ready should be under 5% but for cluster i don know.



  • 6.  RE: cpu ratio

    Posted Sep 18, 2020 11:37 AM

    Again, it depends and each environment is different.
    A CPU% Ready of 30 and higher normally indicates congestion.

    Have a look at PERFORMANCE TROUBLESHOOTING – CPU READY TIME