Red Hat Enterprise Linux Server Cookbook

Adding CPUs on the fly

Imagine an enterprise having to correctly add dimension to all their systems right from the start. In my experience, this is very difficult. You will either underdimension it, and your customers will complain about performance at some point, or you will overdimension it, and then the machine will sit there, idling about, which is not optimal either. This is the reason hardware vendors have come up with hot-add resources. This allows a system to have its CPUs, memory, and/or disks to be upgraded/increased without the need for a shutdown. A KVM implements a similar functionality for its guests. It allows you to increase the CPUs, memory, and disks on the fly.

The actual recipe is very simple to execute, but there are some prerequisites ...