VMWARE ESXi hypervisor phyicsal core allocation overhead

[jefbatso]

I'd like to know how many physical cores worth of CPU cycles ESXi 5.5 hypervisor reserves so that it can function as expected. I cant seem to find this information documented anywhere. I found documentation on memory overhead for ESXi. Nothing for CPU :smileysad:.

Is there a rule of thumb that can be used for planning?

[bayupw]

Hi

Do not plan on fully utilizing host CPU resources. I would normally propose 80% of maximum host utilization.

Leave some headroom for such things as:

- Short-term utilization increasing as part of the  normal business cycle

- Accommodating hardware maintenance and  host patching

- Accommodating failover in a vSphere  High Availability cluster

- Accommodating failover from other datacenters  during disaster recovery

- VMkernel overhead

- Future growth

e.g. you have 10 cores of 2.5GHz per host, total = 25GHz per host. If you plan for 80% max host utilization, then your available CPU per host is 20GHz.

Then you can calculate what is the total CPU required for total VMs at peak, divide it by 20GHz then you will get the number of ESXi host required, similar for memory.

[jefbatso]

Thanks for the information. Do you know if this is documented by VMware as a best practice?