Max recommended vCPUs for a VM

[rz1]

Hello all,

A version of this question has been asked many times, but in searching the forums, I couldn't find this specific question, so hopefully I'm not duplicating discussions.  Here goes:

I have a cluster of identical ESX servers.  They are HP DL380 G6's, two quad core processors.  Here's what the Processor properties shows under the configuration tab:

Model                        Intel(R) Xeon(R) CPU X5660 @ 2.67GHz

Processor Speed       2.7GHz

Processor Sockets     2

Processor Cores per Socket     4

Logical Processors     16

Hyperthreading          Enabled

I want to provide a vm with 8 CPU's.

I understand it is not advisable to configure a vm with the same number of processors as the physical machine, partly because the Service Console needs someplace to run and partly (or in addition) it will cause scheduling issues.  My question is that when I say "the same number of processors as the physical machine", is that 8 in this case (or 16)?  Does hyperthreading apply to this advise?

[weinstein5]

The host will have 16 LCPUs to schedule against so you should be ok as long as there is not a high CPU load on the host - Why does the VM need 8 vCPUs?

[eeg3]

Will you be putting other VMs on this host, or is this going to be a 1 VM to 1 Host setup? It is recommended to stick with only as many vCPUs as you need for performance due to CPU scheduling. You can actually end up with less performance by giving a virtual machine too many vCPUs.

[Troy_Clavell · Accepted solution]

The only way you can provide 8 vCPU to a guest in vSphere4 is to have Enterprise Plus Licensing.  If you do, I would say start with what the application/server "needs".  Maybe 2vCPU and go up from there as performance demands.

If you have 16 logical CPU's and give your guest 8, you are not overcommiting, if this is the only guest running on the ESXi Host.  Also, for ESXi, there is no Service Console.