A host is deemed non-responsive when the Red Hat Enterprise Virtualization Manager cannot communicate with the Red Hat Enterprise Virtualization agent on the host. This can be either due to a networking issue, or failure on the host side (kernel panic, power failure and such) which stops all communication with the host.

When a host is non-responsive, it will be fenced to ensure that virtual machines are allowed to restart on other hosts in the cluster while avoiding "split brain" -- a situation in which communication with the host is lost while the virtual machines are still partially running. This scenario is simulated in the following section, where you will disconnect the host's management network while the storage connection remains functional.

At this stage, the Pacific host is non-operational as its storage connection was cut in the previous section.

Restart it for the next demonstration. On the Tree pane, select the Pacific host. Click the Power Management button and select Restart. Because you have fenced the host, it automatically brings the storage and p1p1 networks up again, and allows the host to run as normal.

When the host's status changes to Up, migrate several machines onto it. This example uses RHEL6RioGrande, RHEL6Thames (both highly available machines) and RHEL6Erie. As you have disabled cluster policy at the beginning of this lab, these virtual machines will not auto-migrate as soon as the host is back up. Therefore, they need to be manually migrated to the Pacific host.