The Dell Precision M6400 Mobile Workstation Supports Single and Dual Drive Configurations. (Two 2.5" Solid State Drive or Hard Drives) Note: If installing the primary 2.5" Drive, you will need the 2.5" Drive (HDD1) primary drive caddy p/n N361F for installation. If Installing the secondary 2.5" Drive, you will need the 2.5" Drive (HDD2) secondary drive caddy p/n J501F and interposer connector p/n FP2P7 for installation.