Physical CPU to vCPU

[Dary]

Hi All,

What is the relations of Host physical CPU to Guest vCPU?
i.e. if a Host has 2 physical CPUs, how many guest VM I can create, and how many vCPU I can assign to each guest?

Thanks in Adv.
Dary

[Torsten.]

If you have 2 physical, you can also have up to 2 virtual cpus (per guest).

[Dary]

Can I have more then 2 guest? I know I can have one guest with more then one vCPU.

what I need to know is, the relation of physical CPU to vCPU is it 1:1 or 1:many?

or vCPU is just a subset of a physical CPU? and it has nothing to do with the actual physical CPU on the host.

[Torsten.]

to quote the manual:

"Every virtual machine has at least one vCPU. A running virtual machine cannot use more vCPUs
than the number of physical CPUs on the VM Host system. (For the purpose of this discussion,
the term â physical CPUâ refers to a processing entity on which a software thread can be
scheduled.)"

If you configure more, the VM will not start.


"how many guests" is a question of the entitlement. see manual section

3.2.4 Entitlement

[Tim Nelson]

Discounting the performance requirements of each, here is my math.

If 2 phys CPU , and entitlement of 5% for each VmGuest:

40 1 vCPU guests can be created. (5 *20 = 1 vCPU)

or

20 2 vCPU guests can be created.

but wait.....

VMGuest needs some RAM.

Takes at least 1GB to run hpux 11.23.
Add an application with some RAM requirements.


Moral:
Ram is typcially the limiting factor.

[Russell.Wood]

Based on your reasoning above, would it be 5% entitlement across two CPUs or 5% on each CPU (thereby making it 10%)?

[likid0]

its 5% on each CPU.

So if you give the VM 2 vcpus, and 5% ent. You are getting 5% of each cpu.