This hard drive from Western Digital has room for 6 TB of data. It has a 5 400 rpm rotation speed.
From Amazon
Western Digital Purple 6TB Surveillance 3.5 Inch SATA 6 Gb/s Hard Disk Drive with Allframe 4K Technology - 180TB/yr, 64MB Cache, 5400rpm - WD60PURZ
AA2Z Supply
WESTERN DIGITAL WD60PURZ WD PURPLE 6TB 5400RPM SATA-6GBPS 64MB BUFFER 3.5INCH INTERNAL SURVEILLANCE HARD DISK DRIVE. BULK. .
EE Store
WD 6TB Purple 3.5 SATA 6Gb/s 5400RPM 64MB Surveillance Drive
Electrical World
Western Digital WD Purple Hard Disk Drive - 6TB