Configuring the HA feature
The vSphere HA feature offers additional protection for virtual machines running on a cluster. There are three scenarios it can handle:
Restart VMs on another host in case of host failure; this requires host monitoring.
Restart a VM in case of guest OS failure; this requires VM monitoring.
Reset a VM in case of application failure; this requires application monitoring.
HA is a cluster setting that applies to all running VMs. Once enabled, it protects all virtual machines and allows administrators to adjust additional settings such as VM prioritization and monitoring settings.
vCenter Server is required to configure the feature. It's not required for HA to operate and once the feature is enabled, it works even if vCenter is down.
Host monitoring prevents ESXi host failure. When it's enabled, HA monitors the host's heartbeats. If heartbeats are not received within a certain period of time, HA restarts VMs on another host.
VM monitoring is a protection against guest OS failure...
