What function does vMotion perform in VMware vSphere?

vMotion is a key feature in VMware vSphere that allows the live migration of running virtual machines (VMs) between ESXi hosts with zero downtime. This functionality is essential for maintaining high availability and resource optimization without interrupting the services provided by the virtual machines.

During a vMotion operation, the state of the VM is moved from the source host to the destination host while the VM continues to run. This process involves the transfer of the VM’s memory and CPU state, ensuring that users do not experience any disruption or service interruption. This is particularly beneficial for tasks such as load balancing, hardware maintenance, or recovery from host failures, as it allows administrators to manage resources effectively while optimizing performance and availability.

The other options do not accurately describe the primary purpose of vMotion. For example, migrating virtual machines between physical storage devices pertains to storage vMotion, which is a distinct feature, and that's why it does not relate directly to vMotion. The function related to compression and storage management does not connect to the vMotion capabilities since it specifically targets live migration rather than storage efficiency. Lastly, balancing storage allocations across datastores is more aligned with storage management tools rather than vMotion's focus on the seamless movement of virtual machines across physical servers.