Advice : Maximum VCPU

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Advice : Maximum VCPU

Postby hdrapin » 1. May 2010, 14:42

Hi,

I have an iMac with a core i7, this is a 4 core with (more) 4 "virtual" CPU. My computer have "virtually" 8 cores.

Question 1 : In VirtualBox (3.1.6) I can use up to 16 VCPU on virtual Machine, does it means that; for all VM, VirtualBox will double the number of physical CPU/Core ?

Question 2 : Starting in version 3.0 the maximum number of VCPU is 32.. does it make sens to have more than 1 or 2 VCPU on virtual machine ?

My understanding is : until we won't be able to dedicated one VPCU to one CPU, the "load" on processor will be split on several CPU, not on only one. So using several VPCU doesn't have benefits ?

What is the best practice regarding the number of VCPU ?

Many thanks
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Re: Advice : Maximum VCPU

Postby Technologov » 2. May 2010, 10:55

>Question 1 : In VirtualBox (3.1.6) I can use up to 16 VCPU on virtual Machine, does it means that; for all VM, VirtualBox will double the number of physical CPU/Core ?

Yes, it means your host cores will be over-committed.

>Question 2 : Starting in version 3.0 the maximum number of VCPU is 32.. does it make sens to have more than 1 or 2 VCPU on virtual machine ?

In some cases, yes (mathematics or server load). In most cases, not (desktop load).

>My understanding is : until we won't be able to dedicated one VPCU to one CPU, the "load" on processor will be split on several CPU, not on only one. So using several VPCU doesn't have benefits ?

The total load of all guest VCPUs will be split among the real CPUs.

>What is the best practice regarding the number of VCPU ?

IMO VCPUs should not exceed logical CPUs on your host.

-Technologov
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