Adding a New Media server to Deduplication

Hi,

I'm not sure if this is related to NetBackup or Puredisk...
Here is my setup:

One NetBackup Master Server 7.0
One PDDO server (PDOS 6.6)

Media server used for deduplication is the master itself, and it's causing a lot cpu usage... That's why we have decided to add a new media server for deduplication... Installa NetBackup 7.0 to that server as media server.

When i try to choose new media server on "Media and Device Management" -> "Credentials" -> "Storage Servers" -> pddo.local (Change) -> "Login Credentials"
It gives the following error:
"Add credentials failed for media server/s:
media_server: Unknown error(-1)"

What i need to know is, am i missing something before that step? How can i add a new media server to use for deduplication on the same server and same disk pool, or is it even possible? Do i need to re-create all of "Storage unit", "Disk pool" and "Storage server"???