UTC MTBF has a lot of meaning but it does not mean the device will last 136 years All of these misunderstandings are really surprising And it does not mean that you will not see a failure in home use Saying you will never see a failure is just dumb What does it really mean It means that one out of every 136 devices will have a mechanical failure every year Or equivalently if there were 1360 devices spinning then on average 10 would mechanically fail every year That is the meaning of 1 2 million hours But this needs to be put into context Infant mortality is not counted because those devices never were in use Software failures user failures infrastructure failures brownouts heat and overheating and viral or deliberate attacks are not counted either So a home user is still going to see the failure every few years Even with enterprise drives What the home user should not see is driving the drive to death It should be built for continuous action of the head and that action not fail for on average 1 2 million hours 21 43 9 February 2014