4.1. Introduction to Power Management and Fencing
The Red Hat Virtualization environment is most flexible and resilient when power management and fencing have been configured. Power management allows the Red Hat Virtualization Manager to control host power cycle operations, most importantly to reboot hosts on which problems have been detected. Fencing is used to isolate problem hosts from a functional Red Hat Virtualization environment by rebooting them, in order to prevent performance degradation. Fenced hosts can then be returned to responsive status through administrator action and be reintegrated into the environment.
Power management and fencing make use of special dedicated hardware in order to restart hosts independently of host operating systems. The Red Hat Virtualization Manager connects to a power management devices using a network IP address or hostname. In the context of Red Hat Virtualization, a power management device and a fencing device are the same thing.