Amazon.com: Western Digital Purple 3TB Surveillance Hard Disk Drive - 5400 RPM Class SATA 6 Gb/s 64MB Cache 3.5 Inch - WD30PURX [Old Version] : Electronics
Amazon.com: WD Purple NV 6TB Surveillance Hard Disk Drive - Intellipower SATA 6 Gb/s 64MB Cache 3.5 Inch - WD6NPURX : Electronics
Introducing New WD Purple NV - What's the difference? - YouTube