Apple has identified a problem in the hard drives of specific older iMacs. 3TB hard drives for 27-inch Macs that were sold between December 2012 and September 2013 could "fail under certain conditions". Mac users affected by the problem are eligible for a special replacement program where the faulty hard drive will be switched out for free. This isn't the first time iMacs have had this kind of problem. In 2011 Apple replaced faulty HDD's from the manufacturer, Seagate.