Using mapped drive letter to point the DFM data is not supported.
You can directly set the option to CIFS path, but after completing the
1. Add a user having privileges on the CIFS share as an “administrator” on the DFM station.
2. Set the DFM Server service “Log On as” user as the above user
3. Set the DFM Scheduler service “Log On as” user as the above user
4. Add this user to the DFM with GlobalFullControl role.
Also see http://now.netapp.com/NOW/knowledge/docs/DFM_win/rel40/html/faq/index.shtml#_9.15
Regards,
Prasad