Western Digital 4TB Purple Surveillance Internal Hard Drive HDD 256MB Cache 3.5" SATA: From the manufacturerWD Purple Surveillance Hard Disk DriveBuilt for 24/7, always-on, high-definition security systems. With a supported workload rate of up to 180 TB/yr and support for up to 64 cameras, WD Purple drives are optimized for surveillance systems.AllFrame 4KTM TechnologyReduces frame lo