Dear all,
Apple has determined that a very small number of 3TB hard drives used in 27-inch iMac systems, may fail under certain conditions. These systems were sold between December 2012 and September 2013. Apple or an Apple Authorized Service Provider (AASP) will replace affected hard drives free of charge.
The program covers affected iMac models until December 19, 2015 or three years from its original date of sale, whichever provides longer coverage for you.
Affected iMac can be checked by serial number as below;