Hi Paolo, thanks for the prompt reply.
On 2014-07-18 17:30, Paolo Bonzini wrote:
Il 18/07/2014 15:06, Riccardo Brunetti ha scritto:
1) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) = total number of
physical
cores (12) (both VMs have < 12 vCPUs) (ie. 8+4)
2) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of
physical
cores (12) (both VMs have <= 12 vCPUs) (ie. 12+8)
3) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of
physical
cores (12) (one VM has > 12 vCPUs) (ie. 16+8)
4) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of
physical
cores (12) (both VMs have > 12 vCPUs) (ie. 16+16)
The last two are usually bad ideas. The first two should be okay.
Overcommitting works best if the VM are I/O bound (disk or network).
If you're overcommitting, hyperthreading should in general be enabled.
So, it should be ok to have the first two options, but also considering
that with hyperthreading instead of 12 cores we can consider 24? Thus we
can go with:
1) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) = total number of cores
(24) (both VMs have < 24 vCPUs) (ie. 18+6)
2) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of cores
(24) (both VMs have <= 24 vCPUs) (ie. 24+10)
Answers for very specific scenarios are hard to give though, so you
should also benchmark your deployment with realistic workloads.
Yes, I understand.
Paolo
Riccardo
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