[one-users] Need some details on CPU/vCPU in Sunstone and capacity planning.

[kiran ranjane]

Hi Carlos,

Thanks for the explanation, Few more question on this :

How many vCPU a core can manage?
What is the maximum vCPU that can be allocated to a VM?

Thanks
Kiran Ranjane


On Thu, Feb 20, 2014 at 9:32 PM, Carlos Martín Sánchez <
cmartin at opennebula.org> wrote:

> Hi,
>
> On Mon, Feb 17, 2014 at 4:29 PM, kiran ranjane <kiran.ranjane at gmail.com>
>  wrote:
>
> Hi Everyone,
>>
>> I have few questions with regards to cpu and vcpu while creating
>> templates in Sunstone :
>>
>> 1) What is the difference between cpu and vcpu according to opennebula
>> architecture?
>>
>
> CPU refers to the physical Host cpu cores, the one you see in the
> "allocated cpu" column.
> vCPU is simply the number of cpus that the VM guest will see, but it does
> not affect the physical resources assigned to the VM.
>
> 2) How do we calculate vCPU, For example if I have 1 processor with 8 core
>> then how much vCPU can I allocate.
>>
>
> They are not related. But the scheduler will not deploy more VMs when the
> sum of the running VM CPU reaches 8.
>
>
>> 3) How can I manage cpu capacity (recommendation) in a better way so that
>> I can utilize it in optimum way.
>>
> 4) Any calculation on CPU or formula that we need to use before assigning
>> it to Virtual machine, For example if I use 1 CPU in the virtual machine it
>> uses 1 core of the processor? is this correct.
>> 5) What is the use of vCPU, If I have allocated 1 CPU and 2 vCPU to the
>> virtual machine thus that mean it will use 1 core of the physical and
>> inside the VM it will show 2 cpu assigned to it?
>>
>
> The purpose of vCPU is to allow cpu overcommitment. For example, for a
> host with 8 cores, you could create 4 VMs with
> cpu=2, vcpu=2
>
> But if your VMs workload is not very cpu-intensive, you could decide to
> launch 16 VMs
> cpu=0.5, vcpu=2
>
>
> To ensure that the VMs are not using more CPU than the amount assigned,
> you may need to configure your hypervisor. For example, in kvm you need to
> configure cgroups [1]
>
> Regards
>
> [1]
> http://docs.opennebula.org/stable/administration/virtualization/kvmg.html#working-with-cgroups-optional
> --
> Carlos Martín, MSc
> Project Engineer
> OpenNebula - Flexible Enterprise Cloud Made Simple
> www.OpenNebula.org | cmartin at opennebula.org | @OpenNebula<http://twitter.com/opennebula>
>
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