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I virtualized a server using VMware ESXi. My virtual machine has 8 vCPU, while the real processor is an Intel Xeon E5-2620 v3 (6 core) @ 2,4 GHz. In order to estimate virtual resources needed for running that virtual machine, is it correct the following calculation? Total amount of GHz = # of vCPU * clock CPU = 8 * 2,4 = 19,2 GHz

Thanks in advance.

Andrea

A M
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    Why do you have more virtual cores than physical cores? Granted, there's hyperthreading on that CPU, so you'll see 12 usable cores at the host level. But don't you think there's something wrong with provisioning so many virtual cores? Is this the only virtual machine on the host? – ewwhite Jul 11 '16 at 14:13
  • It's just a stress test. Yes, there is hyperthreading and that is the only virtual machine. I'm studying minimum virtual resources needed for executing that virtual machine. – A M Jul 11 '16 at 14:20
  • Your minimum resources for that VM (without major scheduling contention) would be 8 available cores. The GHz may not matter. – ewwhite Jul 11 '16 at 14:25
  • And if I want to calculate GHz? – A M Jul 11 '16 at 14:27
  • I'm not sure. I don't have an answer for that. – ewwhite Jul 11 '16 at 14:28
  • It's an assumption... but in WMware ESXi, I can see a chart representing the CPU usage, in terms of % and also of GHz. So, for example, in that chart, a 5% CPU usage corresponds to 961 MHz, meaning that 100% corresponds to 19,2 GHz. The calculation Total amount of GHz = # of vCPU * clock CPU returns the same result. – A M Jul 11 '16 at 14:35
  • Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/42328/discussion-between-andrea-monopoli-and-ewwhite). – A M Jul 11 '16 at 14:41

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The VMware vSphere documentation (https://pubs.vmware.com/vsphere-60/index.jsp#com.vmware.vsphere.monitoring.doc/GUID-FB4C372B-49AC-4A0F-8573-D8E23241570A.html), about CPU charts said:

Amount of CPU actively used by the host, resource pool, or virtual machine in the cluster.
■ Counter: usagemhz
■ Stats Type: Rate
■ Unit: MegaHertz (MHz)

So, it seems in the chart representing CPU usage of virtual machine, it gives informations about consumption; therefore, as I said in the previous comment, in that chart, a 5% CPU usage corresponds to 961 MHz, meaning that 100% corresponds to 19,2 GHz.
On the other hand, from the same type of chart applied to the host I can see a 6,96% usage corresponds to 1000 MHz used, which means 100% corresponds to 14,4 GHz. And 14,4 GHz is also the result of the calculation:
Total amount of GHz = # of CPU * clock CPU = 6 * 2,4 GHz= 14,4 GHz, where 6 is the number of cores of the real processor.
I think the answer is in the CPU usage charts.

A M
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