comparison of physical CPU and vCPU cores

Hello

I'm an admin of VMWare and recently asked by a customer in our Cloud Computing environment to add an extra vCPU to one of their virtual machines so that it aligned the physical counterpart that they had migrated away from more.  The physical version had 2 processors quad core (clocked at 1.4 Ghz) and the virtual version has now 2 vCPUs (The ESXI host a 2.4 Ghz CPU).  Since then, I've been asked how to compare the two and I am struggling to explain their project...

The user connects to the physical computer and run the Task Manager and sees the 8 cores working away

It then records in the virtual machine and see the two processors working away.  You can say that he thinks that the performance piling in ESXi...

How to compare the two scenarios and how can I explain that is comparable in an ESXi environment - and is it really comparable?

The way I see it, adding a second processor on the virtual computer which means provide 2 physical processors on the host are available, instructions can be performed on them by the customer, which means that 2 at the same time.

On the physical server, the 8 cores can be used simultaeously then, how this can never be comparable?

Or I have this completely wrong?  Performance and the remains has never been my strong point!

Advice or answers on the above would be welcome

Thank you

Hello.

Each vCPU is mapped to a logical processor, which is a physical on your host system kernel if you do not have active Hyperthreading.

I don't like the physical to virtual comparison, but of course I know my clients.

In most cases, the physical resources have never been effectively used, as the operating system or application running on the top was not able to use the 8 cores of the two processors for example four hearts in your example.

So most of the time you can get the same performance with only 1 or 2 vCPUs after moving to virtualization.

If you want to know more you can read the resource management Guide: http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-501-resource-management-guide.pdf

Concerning

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