Which feature allows ESXi hosts to respond quickly to system failures?

High Availability (HA) is specifically designed to ensure that virtual machines remain operational and available in the event of host or hardware failures. When HA is configured within a vSphere environment, it continuously monitors the health of ESXi hosts and the VMs running on them. If a host fails, HA can automatically restart the affected VMs on other available hosts within the cluster, minimizing downtime and maintaining service availability. This process is automatic and requires minimal administrator intervention, which allows for a swift response to system failures.

The other options, while valuable in their own rights, do not specifically address the immediate response to system failures:

• Storage DRS is focused on optimizing storage resources by balancing loads and managing space efficiently, rather than responding to host failures.

• A Distributed Switch provides advanced networking features for virtual machines and simplifies network management, but it does not play a role in recovery from host failures.

• Content Library is concerned with the management and distribution of virtual machine templates and ISO images, which does not relate to the quick response required during a failure scenario.

Thus, High Availability stands out as the feature explicitly designed to enhance system resilience by enabling rapid recovery from failures.