Which feature helps maintain zero data loss when a VM on an ESXi server fails unexpectedly?

Fault Tolerance is designed specifically to provide continuous availability for virtual machines, ensuring zero data loss even during an unexpected failure of the ESXi server hosting that VM. When Fault Tolerance is enabled for a VM, it creates a live shadow instance of the VM on a separate ESXi host. This shadow instance is fully synchronized with the primary VM, ensuring that every transaction is replicated in real-time. In the event of a failure, the system can automatically and seamlessly failover to the shadow VM without any downtime or loss of data, thus maintaining the integrity and availability of the application running within the virtual machine.

While other features such as vSphere High Availability, Storage vMotion, and vMotion enhance availability, resource management, or migration of VMs, they do not specifically ensure zero data loss during an unexpected failure of the ESXi server. vSphere High Availability, for instance, can restart VMs on another host after a failure, but there could be data loss depending on the state of the VM at the time of the failure.