Duplicate data on Virtual tape to Physical tape

Gurus,

 I am using NDMP accelerator to backup data on Isilon ( NAS) to DataDomain VTL, then need to  duplicate the data from VTLto physical library. The Isilon is connected to the physical tape drives. Can I configure the physical storage unit on the Isilon/NDMP host? Or do I need to find another Media server to configure the physical storage unit on that Media server? I would like to use the NDMP direct copy feature. VTL tape is LTO 4, Physical tape is LTO 6. Will it have any problem if they are different? Please let me know how to make it work.

Thanks!