Seagate Skyhawk 4TB 7200 RPM Surveillance 3.5 Inch SATA Desktop Internal Hard Disk Drive ( ST4000VX013 )

Western Digital Purple 2TB 3.5-Inch SATA Surveillance Desktop Internal Hard Disk Drive ( WD23PURZ )
Engineered for mainstream surveillance systems
WD AllFrame technology delivers optimizations for write-intensive, low bit-rate, high stream-count workloads typical to mainstream surveillance applications
Supports up to 180TB/yr workload rate and up to 16 bays