The exponential lifetime distribution is the model for ideal memoryless failures: the probability of failure in a dt interval is independent of current lifetime

The exponential lifetime distribution is the model for ideal memoryless failures: the probability of failure in a dt interval is independent of current lifetime and have value lambda*dt. Those are as "random" failures as they get. I suppose hard drives are better modelled by a variable failure rate lamba(t), which should have a peak for the first few hours/days, settle down and then start growing quickly after a few months.