"David Sekne" <david.sekne@gmail.com> writes:
Hello,
I recently upgraded our cluster from 4.3 to 4.5 (4.5.1.3-1.el8), I raised the cluster compatibility afterwards to 4.7 as well. I noticed that the CPU hot plugging does not work above 16 CPU's if cluster compatibility is set to 4.6 or 4.7.
Error I get is: Failed to hot set number of CPUS to VM testVM-3. Underlying error message: invalid argument: requested vcpus is greater than max allowable vcpus for the live domain: 32 > 16
Issue here I believe is that the MaxNumOfVmSockets values set on the engine per cluster version is not correctly set on libvirt when VM is started.
My values on the engine: MaxNumOfVmSockets: 32 version: 4.2 MaxNumOfVmSockets: 32 version: 4.3 MaxNumOfVmSockets: 32 version: 4.4 MaxNumOfVmSockets: 32 version: 4.5 MaxNumOfVmSockets: 64 version: 4.6 MaxNumOfVmSockets: 10000 version: 4.7
Values on libvirt for VM's for all cluster compatibility versions:
4.3 <vcpu placement='static' current='4'>32</vcpu>
4.4 <vcpu placement='static' current='4'>32</vcpu>
4.5 <vcpu placement='static' current='4'>32</vcpu>
4.6 <vcpu placement='static' current='4'>16</vcpu>
4.7 <vcpu placement='static' current='4'>16</vcpu>
Is anyone else experiencing this issue (possible BUG)?
It's most likely a feature. Starting with 4.6, the maximum number of vCPUs is limited because it consumes resources even if the CPUs are not plugged in. Adjusting sockets/cores/threads configuration of the VM to put more than one vCPU on a socket or changing MaxNumOfCpusCoefficient config value should help in your case. Regards, Milan