Western Digital RE WD4000FDYZ 4TB 64MB Cache 7200RPM SATA 6.0Gb/s 3.5″ Internal Enterprise Hard Drive – w/ 1 Year Warranty

Designed for quality and reliability - With a field-tested 1.2 million hour MTBF, this high performance drive delivers the highest level of reliability for 24x7 operation in up to 100% duty cycle applicationsIndustry's highest capacity nearline drive - WD