Unable to allocate 2 CPUs to VM on Workstation server

[ST6]

Hi guys,

I installed VMware Workstation Pro 17 on a Windows server 2016 equipped with two 6-core CPUs.

I tried to assign vCPUs to a virtual machine with 2 processors and 6 cores, but I got the error: "Powering on the virtual machine will fail because it is configured to use more virtual processor cores than the host supports." is displayed and the settings cannot be completed.
When I adjust the number of processors and cores so that the total is 6 cores, the settings are successfully completed and I can start up. However, as a matter of course, only 6 cores of the physical CPU are used.

When I check the Windows Device Manager, it recognizes two 6-core CPUs, for a total of 12 cores, so I don't know why 12 cores aren't allocated.

If anyone has any knowledge, I would appreciate it if you could help me.

Regards,
Tak

[ThompsG]

Hi @ST6,

Is it possible to do three things:

1. Let us know the make/model of the server running Windows 2016?
2. Open Device Manager and confirm that there are no 'unknown' devices.
3. In Device Manager, open the Processors section and confirm the number 'seen' here.

Kind regards.

[ThompsG]

Sorry, not a rant, just simply pointing out the limitations or rather effect, between two possible installation types and how none of the limitations are socket/core counts. This would cover the possible media types which might have been used to install the OS that I can think of and am familiar with. 

Concerning the link provided, the issue I have is that we don't know what edition of Windows 2016 was originally deployed. If they had deployed Windows 2016 Essentials, then that is limited to 2 sockets but unlimited cores. This might explain why they were only able to access 2 sockets worth but after licensing, more were available.  NB: This also has changed with Windows 2022 and is now 1 socket and 10 cores so a severe restriction from previous version of this Windows edition.

Kind regards.

[ST6]

Hi guys, Happy New Year.

Sorry for the late reply.

In the example URL shown by bluefirestorm, the number of CPUs and cores far exceed the number of standard licenses, so it doesn't seem to be directly related to this incident, but what do you think?

It is my understanding that Windows Server 2016 Standard covers up to 16 cores per physical server. I feel like there is no problem with 2 CPUs and a total of 12 cores.

[bluefirestorm]

The Spiceworks link is an example of wrong licensing and results in the same symptoms as you what you have.

As stated earlier, verify the license that you have; ask the vendor or check using slmgr /dlv on the Windows command line

If you want to go extreme, try running Prime95 on the Windows Server 2016, and see whether it allows you to use all 12 cores. Then as a comparison boot up with Linux USB as Linux does not have licensing restrictions on CPU cores, and run Prime95 on Linux and see if you can run with all 12 cores. If you really want to go super extreme, you can install a Linux partition on the same server (Ubuntu Desktop lets you partition for dual boot between Ubuntu and Windows) and install Workstation on Linux and see if you can create a VM with 12 cores.

[ThompsG]

@ST6,

You are correct. There isn't an issue with licensing unless you are running 'Essentials' edition (Hardware limits for Windows Server Essentials | Microsoft Learn) which you have already confirmed you aren't. Even if Windows licensing restricted cores to the product key you entered (it doesn't and hasn't that I can recall except for limits based on edition) then 16 cores are the minimum you can purchase and over the 12 cores you have.

Is it possible to list the make/model of the server?

Kind regards.