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Virtual Machine CPU Hot Add And Memory Hot Plug Features Are Grayed Out

This is was one of the issues commonly raised by few clients after updating their environments and deployed Virtual Machines CPU Hot Add and Memory Hot Plug features are grayed out in the Virtual Machine settings and were not able to enable them. Some of the engineers tried to power off the Virtual Machines and tried the same but it didn’t make any difference to the features. So I thought to write this article in my blog to share this with the others. 

These features are quite useful for the high memory demanding applications running Virtual Machines in order to increase the Virtual Machine resources without a downtime. If you check these features and if those are grayed out do not confused and check few things in your Virtual Machine. 

CPU Hot Add And Memory Hot Plug Features Are Grayed Out : Grayed Out

This issue mainly occurred due to the Operating System Compatibility and the Virtual Machine was incorrectly select the unsupported Operating System when installing the Operating System. In my case deployment engineers used a different tool to deploy the bulk Virtual Machines and misconfiguration of the tool caused the issue. 

Note: Minimum Virtual Hardware version should be 7 in order to compatible with CPU Hot add and Memory hot plug. Compatibility can be checked in this VMWare Guest OS Compatibility Guide


CPU Hot Add And Memory Hot Plug Features Are Grayed Out : Incorrect OS

Incorrect OS was selected and that caused the issue

Changed the Virtual Guest OS in the “VM options” to the relevant version and that enabled the features again

CPU Hot Add And Memory Hot Plug Features Are Grayed Out : VM Options

If you get similar issues make sure to check the OS compatibility and the Virtual Hardware versions accordingly. 

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Aruna Lakmal

Associate Technical Specialist at Pearson, Sri Lanka. Technology junky, enthusiast, a VMware vExpert and a blogger with more than 7 years of Experience in Information Technology more focusing on VMware Virtualization, Microsoft and Datacenter Technologies.

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