VM Hot Add CPU Or Memory

Private Cloud Director supports hot-add of CPU and / or memory resources to a running virtual machine. Using this feature, you can increase CPU cores or memory allocated to a running VM, without having to power-cycle it. This is valuable for production VMs that need more resources to meet workload demands but that can not be powered off.

Pre-requisites

• Read more here about Zero-Size Flavor. Using zero-size flavor when creating your VM is a requirement for hot-add. Before you can hot-add CPU or memory resources to a VM, the VM must have been created using zero-size flavor.

Hot-add CPU or Memory to a Running VM

1. Select a powered-on VM that was created with a zero-size flavor.
2. On the VM grid view, navigate to ▷ Other Actions ▷ Hotplug.
3. Enter the new vCPU and/or memory value for the VM. The maximum allowable values are automatically set based on the VM configuration.
4. Click Hotplug VM.

Limitations

• Hot add can only be used to increase the current CPU or memory allocation of a running VM. Reducing currently allocated CPU or memory is supported only while the VM is stopped.
• You can not use the hot-add feature to resize the disk of a running VM today.
• On VMs running Windows Server 2022, the guest OS's System Information (systeminfo) may display the flavor's maximum configured hotplug memory value instead of the VM's current memory allocation after a memory hot-add operation.
• Hot-add-capable VMs that boot from a persistent volume and were created before the PCD 2025.10 release may fail to live migrate until a one-time corrective hotplug is applied. See Resolve Live Migration Failures for Legacy Boot-from-Volume Hotplug VMs.