WD 6TB Purple 5400 rpm SATA III 3.5" Internal WDBGKN0060HNC-WRSN
Amazon.com: Seagate SkyHawk 6TB Surveillance Internal Hard Drive HDD – 3.5 Inch SATA 6GB/s 256MB Cache for DVR NVR Security Camera System with Drive Health Management – Frustration Free Packaging (ST6000VX001) : Electronics
WD 6TB Ultrastar DC HC310 7200 RPM SATA 3.5" Hard Drive (0B36039)