In Nutanix AHV-based clusters, when you want to ensure that a specific VM (e.g., a critical VM like a domain controller) is powered on before other VMs during a host startup or failover scenario, you use the Agent VM configuration setting.

Here's the exact explanation from the Nutanix ECA course:

''Agent VMs are special VMs that are automatically powered on before other user VMs during host startup or recovery. This ensures that critical VMs, such as those that provide essential services, are always available first.''

In contrast:

Recovery Plan (A) --- This is used in the context of DR and failover, typically with Nutanix Leap.

Host Affinity (B) --- Host affinity rules control placement policies of VMs but not startup priority.

High Availability (C) --- HA ensures VMs are restarted on surviving hosts but does not control startup order.

Therefore, setting the VM as an Agent VM guarantees that it is powered on before the other VMs during host start-up. Let me know if you'd like steps on how to configure an Agent VM within Prism Central or Prism Element!