Toshiba P300 4TB 128MB 6.0 Gb/s SATA III PC Internal Hard Drive - HDWD240UZSVA
Seagate Skyhawk ST4000VXZ16 4TB Internal Hard Drive HDD Video Recording up to 64 Cameras 3.5" 64MB Cache SATA 6Gb/s Silver FFP Includes 3 Year Rescue Service : Amazon.co.uk: Computers & Accessories