Collector: Questions on vCPU/CPU calculation and calculated CPU count

  • 17 April 2023
  • 5 replies

Hi! I have two doubts related to Collector´s vcpu and cpu calculation.

1) I couldn't find the information on the vcpu/cpu ratio per VM in Collector's Excel spreadsheet? Please, how is it calculated when we perform workload upload per VM?


2) In Sizer, I performed a manual modeling from Collecto´s Excel spreadsheet information as a “Raw Input” and compared it to the automatic per VM-upload modelling.

In the analyzed scenario, the customer has 440 CPU Cores distributed in 19 physical servers/hosts in the current environment (vhost table information)



My calculations/modelling for a “Raw Input” is the same for the overall resources calculated by the automatic per VM upload (RAM, Datastore), except for the total o CPU cores in the cluster.

The automatic per-VM upload/calculation was performed with the following settings:


As result, the workload was modeled with 552 CPU cores:



Please, why does the per-VM upload have 100 more CPU cores than the existing customer´s environment (552 vs 440 from the current environment)?

This ends up resulting in processors with a higher number of cores than are consumed by the customer´s current VMs/workloads. And it generates a more expensive configuration.


Luiz Serrano.

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5 replies

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Hello @Luiz Eduardo 

1- vcpu to pcpu ratio is configured automatically when you choose "provision" when import rvtools or collector sheet, if you create the workload, the ratio is based on the workload itself, for example database is 1:1 or 2:1, regular VM is 4:1 or 6:1.

2- regarding the output the number of cores are different depend on the processor model, more GHz less cores is needed. Also default processor selection affect the number of needed cores, default processor should be the existing customer used processor.

Thanks, Moustafa.

1) Okay, got it. The vcpu/cpu ratio is estimated according to the workload and not necessarily taken from the spreadsheet.

In this case, wouldn't an entry like RAW Input be more accurate than an automatic upload per VM, with an estimated vcpu/cpu ratio? The average vcpu/cpu ratio is 3.85 for this scenario.


2) I think the customer's processor is too old to be selected as “default processor” - Intel(R) Xeon(R) CPU E5-2650 v4 @ 2.20GHz and discontinued.

For me, it makes not much sense to select an Intel Gold processor and get more CPU Cores than a 2650 for the same workload - 552 vs 440.

I believe that fewer cores should be considered in the automatic modelling, raising the vcpu/cpu ratio based on the pass-mark of each processor, for sample.

Or deliver an indicator to the customer in the Sizer report of how much better the performance will be in relation to the current environment to justify the investment.




Userlevel 1

@Luiz Eduardo can you please share the Sizer scenario and the RVTools output to

Hi Arun! Thanks, I am sending the files and the sizer report. Sincerely, Luiz Eduardo.

Thanks, Nutanix Sizer team, for the support and answers! Sincerely, Luiz Eduardo.