What feature allows for the migration of VMs without downtime?

The feature that allows for the migration of virtual machines (VMs) without downtime is vSphere vMotion. This capability enables administrators to move running VMs from one physical host to another without affecting the availability of the applications running on those VMs. During the vMotion process, the memory and execution state of the VM are transferred seamlessly, ensuring that the VM continues to operate without interruption.

This feature is particularly valuable in environments where load balancing, maintenance, or hardware upgrades are necessary since it allows for resource optimization without impacting application performance. With vMotion, there is no impact on the user experience, making it a critical tool for maintaining service continuity in a VMware environment.

In contrast, while features like High Availability and Fault Tolerance enhance VM reliability and minimize downtime in different contexts, they do not specifically facilitate live migration without downtime as vMotion does. Enhanced vMotion Compatibility is an extension that allows vMotion to occur across different versions of ESXi hosts, but it still relies on the fundamental capability provided by vMotion for the actual migration process.