Which two components are critical for enabling HA in a vSphere environment?

For High Availability (HA) to function effectively in a vSphere environment, it is imperative to have both a Cluster and ESXi Hosts configured.

A Cluster in vSphere is a collection of ESXi hosts that are grouped together to provide resources and functionalities such as resource allocation, load balancing, and, importantly, HA. The HA feature works by allowing virtual machines to restart automatically on other available hosts within the same cluster in the event of a host failure. This ensures minimal downtime and increases the availability of virtual machines.

ESXi Hosts are the physical servers that run the virtual machines. They must be part of the cluster for HA to be implemented since HA relies on the hosts' ability to monitor each other's health and the ability to restart the virtual machines on functional hosts if one fails. Without both the cluster and the ESXi hosts working together, HA cannot be established, as there would be no framework to facilitate the automatic restart of VMs or health monitoring of the hosts.

The other options do not encompass both necessary elements for enabling HA. While datastore and resource pools contribute to resource management within the virtualization environment, they do not directly facilitate the HA mechanism.