vSphere Replication has certain operational limits.
To ensure successful virtual machine replication, you must verify that your virtual infrastructure respects certain limits before you start the replication.
You can only deploy one vSphere Replication appliance on a vCenter Server instance. When you deploy another vSphere Replication appliance, during the boot process vSphere Replication detects another appliance already deployed and registered as an extension to vCenter Server. You have to confirm if you want to proceed with the new appliance and recreate all replications or shut it down and reboot the old appliance to restore the original vSphere Replication extension thumbprint in vCenter Server.
Each vSphere Replication management server can manage a maximum of 500 replications.
See http://kb.vmware.com/kb/2034768 for more information.