The following example illustrates how you can change resource allocation settings to improve virtual machine performance.

Assume that on an ESXi host, you have created two new virtual machines—one each for your QA (VM-QA) and Marketing (VM-Marketing) departments.

Figure 1. Single Host with Two Virtual Machines

In this example, a single host has two virtual machines.

In the following example, assume that VM-QA is memory intensive and accordingly you want to change the resource allocation settings for the two virtual machines to:

  • Specify that, when system memory is overcommitted, VM-QA can use twice as much memory and CPU as the Marketing virtual machine. Set the memory shares and CPU shares for VM-QA to High and for VM-Marketing set them to Normal.
  • Ensure that the Marketing virtual machine has a certain amount of guaranteed CPU resources. You can do so using a reservation setting.


  1. Start the vSphere Client and connect to a vCenter Server system.
  2. Right-click VM-QA, the virtual machine for which you want to change shares, and select Edit Settings.
  3. Select the Resources tab, and in the CPU panel, select High from the Shares drop-down menu.
  4. In the Memory panel, select High from the Shares drop-down menu.
  5. Click OK.
  6. Right-click the marketing virtual machine (VM-Marketing) and select Edit Settings.
  7. In the CPU panel, change the Reservation value to the desired number.
  8. Click OK.


If you select the cluster’s Resource Allocation tab and click CPU, you should see that shares for VM-QA are twice that of the other virtual machine. Also, because the virtual machines have not been powered on, the Reservation Used fields have not changed.