Sanjay -
You could put them on the same loops, given that they're both 6G shelves.
Best practice would be to use separate loops for SATA and SAS shelves.
It would also be best practice to do HA multipath cabling.
I'll hope you have an add on SAS card on those heads ?
For more information see the 'Multipath and Dual-Path Cabling Information' documentation under 'disk shelves' on the NetApp support site.
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff
Independent NetApp Consultant, K&H Research http://www.linkedin.com/in/eugenekashpureff
Senior NetApp Instructor, Unitek Education http://www.unitek.com/training/netapp/
(P.S. I appreciate points for helpful or correct answers.)