vSphere Replication is included for free with vSphere Essentials Plus or higher. vSphere Replication allows virtual machines to be replicated between sites or between datastores on the same site. vSphere Replication leverages Change Block Tracking (CBT) to only replicate changes between the source virtual machines and the replication target.
vSphere Replication appliances are deployed at each site participating in replication. Multiple vSphere Replication appliances can be deployed to improve replication performance.