Western Digital 22TB WD Purple Pro Surveillance HDD SATA 6 Gb/s 7200 RPM 512 MB Cache: 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