The "vSphere HA virtual machine failover failed" alarm is triggered when vSphere High Availability determines there are insufficient resources in the cluster to fail over a virtual machine. Removing a host for maintenance reduced the cluster's available resources, triggering this condition. After the host was re-added, the resource constraint was resolved. However, the alarm state does not automatically clear. The administrator must manually intervene to clear the alarm. The "Reset to Green" action is the correct procedure to manually override the alarm's status and return it to normal (green), signifying that the underlying issue has been resolved.

A. Ignore: This is not a formal action in the vSphere Client to clear an alarm; it would leave the system in a persistent warning state.

C. Acknowledge: Acknowledging an alarm only confirms that an administrator has seen it. It does not clear the alarm or change its color status from warning to green.

D. Disable: Disabling the alarm is a permanent configuration change that would prevent this specific alarm from ever triggering again, which is not the appropriate response to a resolved, temporary issue.

1. VMware vSphere Product Documentation

"vSphere Monitoring and Performance" (for vSphere 8.0): In the section "Acknowledge or Reset a Triggered Alarm

" the documentation states

"You can reset the alarm to clear it and return it to its normal state... Resetting an alarm also clears any acknowledgment for the alarm." This directly supports using "Reset to Green" to clear a resolved alarm.

2. VMware Knowledge Base Article 2004802

"'vSphere HA virtual machine failover failed' alarm in vCenter Server": This article explains the cause of the specific alarm in the question

noting it is triggered by insufficient failover capacity. It confirms that after resolving the underlying resource issue (like re-adding a host)

the alarm must be manually cleared. The procedure described is functionally identical to "Reset to Green".

3. VMware vSphere Product Documentation

"vSphere Availability" (for vSphere 8.0): The section on "vSphere HA Admission Control" explains the conditions that lead to failover resource constraints. This provides the context for why removing a host would trigger the alarm

and implicitly

why re-adding it resolves the condition that needs to be manually cleared.