You can use vSphere Replication to replicate a virtual machine in a single vCenter Server even if the vCenter Server instance has only one host in its inventory.
When you configure replication in a single vCenter Server instance, you can select the source site as the target site for replication. You then configure replication in the same way as for an infrastructure with a source and a target site. For example, you can replicate a virtual machine to a different datastore attached to the same host or another host. vSphere Replication prevents you from using the source or replicated virtual machine's vmdk files as the target of the replication.
The virtual machine name must be unique in the same folder in the vCenter Server inventory. In the recovery wizard, vSphere Replication does not allow you to select a folder if there is already a virtual machine with the same name registered to it. During recovery if there is a virtual machine with the same name, you might see an error message. See Error Recovering Virtual Machine in a Single vCenter Server Instance for more information.
If you install vSphere Replication as part of a vCenter Site Recovery Manager (SRM) deployment, any replications that you configure in the same vCenter Server instance are not visible in the SRM user interface. You can still monitor and manage these replications in the vSphere Replication user interface in the vSphere Web Client.