How to Enable Hot Add CPU and Memory in vSphere

In vSphere, there is a new feature, hot add memory and CPU. This is very cool as downtime can be avoided which is, at least in my company, very helpful during daily operations. This feature is not enabled by default. To enable these features, do the following:

1. Make sure the virtual machine hardware is upgraded to version 7, if it is not, then right click the VM and choose 'Upgrade Virtual hardware'. You can find the hardware version by clicking on the 'Summary' tab.



2. Go to edit settings for the VM, then the options tab, under 'Advanced', select 'Memory/CPU hotplug' and in the pane to the right, enable the memory hot add and CPU hot plug features. This change must be made when the VM is powered down. If the VM is running, the options will be greyed out as in the image below.



Hot add memory and CPU is not supported by all OS's, Windows 2008 Enterprise 64 bit edition is one of the suppoted OS's, for a complete list, take a look at the Guest OS Guide.