UTC  MTBF has a lot of meaning but it does not mean the device will last  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  devices will have a mechanical failure every year Or equivalently if there were  devices spinning then on average  would mechanically fail every year That is the meaning of  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  million hours     February