WD Purple Hard Disk Drive Professional Surveillance 6TB AV 3.5″ 128MB Cache, Engineered specifically for CCTV security systems. Tuned for write-intensive, low bit-rate, high stream-count workloads typical to most Networking Video Recorder(NVR) or Digital Video Recorder (DVR) applications. Supports up to 180 TB/yr. workload rate, Tuned for write-intensive, low bit-rate, high stream-count applications typical to most surveillance applications, Prioritized write-operations for maximized surveillance performance, TLER & ATA streaming support