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Adding CPUs to a VM

Number of views : 9
Article Number : KB0011596
Published on : 2023-11-01
Last modified : 2023-11-01 21:22:23
Knowledge Base : IT Public Self Help

Adding CPUs to a Virtual Machine in UT-VMG

To add CPUs to a virtual machine, go through the following steps. A video demonstration of the process is available below.

  1. Log into the UT-VMG interface.
  2. Navigate to the Virtual Machines menu.


  3. Click the Action menu of the VM.


  1. Click Resize.


  2. Enter the desired number of vCPUs for this VM.

    Important: If you do not want to reboot, you must uncheck Reboot Machine.

    Click Submit.


Notes about Adding CPU

  • ITS-provided blueprints/templates should support hot adding CPUs. If you want to add CPUs without a reboot, simply uncheck the option.
  • Do not change the Cores per Socket.
  • Reducing CPUs always requires a reboot.
  • The change will occur immediately after clicking Submit if the CPU count is below the approval threshold. If the requested number of CPUs is equal to or greater than the approval threshold, the change will occur as soon as it is approved. (By default, approvers are the UT-VMG administrators but if you are using custom blueprints, there may be approvers in your department.)
  • If you chose to reboot, the VM will be shut down, the VM CPUs will be reconfigured, and the VM will be powered back on. If you selected Do not reboot for the Power Action, the CPUs will be reconfigured while the VM runs.

Notes about CPU Ready

Adding too many CPUs to a VM can often impact performance by increasing the CPU Ready metric. In oversimplified terms, this means your VM's vCPU cores are waiting for free time on the hypervisor. We STRONGLY advise limiting how many CPU you add at a time. We recommend adding in steps of 2, and then assessing the performance impact of each change. Remember, you can easily add more vCPU if necessary.


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