With the release of version 5.1, VMware introduced some extra functionality to the vMotion platform. One of these enhancements enables vMotion to run in environments without shared storage.
I heard a lot of names floating around the community, such as X-vMotion, Unified vMotion and enhanced vMotion, but in reality we do not brand this particular enhancement as a separate feature. To give you some background of the previous mentioned terms: X-vMotion was the internal code name for this feature, this name is still visible in the ESXi Host Advanced Setting with the rest of the internal codenames. Unified vMotion is a reference to the unified architecture which combines vMotion and parts of the Storage vMotion for this process. When a virtual machine needs to be migrated between hosts that do not share storage, vMotion copies the data across the vMotion network using some of the Storage vMotion code. A separate article will appear soon expanding on the technical bits of this process.
A separate product name usually means a separate license and that is the beauty of this enhancement. vMotion without the shared storage requirement is available in all kits and edition that have vMotion included. This means, if you are using vMotion today, the moment you upgrade to vSphere 5.1, you can migrate virtual machines between hosts without the need of shared storage and without any downtime.