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XenServer Limit with socket vs vCPU in windows Posted on

The problem is that XenServer virtualises each core as a separate physical processor in its own socket. Windows Server 2008 and 2003 are limited to 4 sockets, so you can only see 4 of your 8 cores in the task manager.

If you look in the Device Manger you’ll see all 8 cores because Windows sees them all, but won’t let you use them.

If you look in the XenServer Host console in the Hardware section, it will report 8 physical CPUs too.

In XenCenter set the VCPUs for your VM to 2.

Then enter the attached code snipped into the XenServer Host console. To find the UUID for your VM, type:

xe vm-list

xe vm-param-set platform:cores-per-socket=4 uuid=xxxxxx

xe vm-param-set VCPUs-max=8 uuid=xxxxxxx

xe vm-param-set VCPUs-at-startup=8 uuid=xxxxxx

Now boot the VM and the task manager should show all 8 cores.

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