WD Purple 1TB 5400RPM 64MB Cache SATA 6.0Gb/s 3.5" Surveillance Internal Hard Drive3. 5 Inch SATA III Designed for Surveillance Up to 256MB Cache The right hard drive choice when you need storage you can rely on to capture every frame in high workload surveillance applications. WD Purple drives have been engineered specifically for the extreme demands of high temperature, 24 7 surveillance systems. Performance you can rely on From a worldwide leader in the storage industry, WD Purple is engineered for quality video playback when you