The largest error in this analysis is the arbitrary picking of a .1% failure rate for some arbitrary time period. In order for this analysis to make sense, it s

The largest error in this analysis is the arbitrary picking of a .1% failure rate for some arbitrary time period. In order for this analysis to make sense, it should be right at the probability of failure for the time period it takes to replicate back to 3 copies. What makes this hard to compute is that drives don't have a linear death rate in regards to age, it's more "bathtub" or `U` shaped. And this number should really be a function of the ages of all the disks. Drives seem to have a sweet spot of reliability after a few months and up until a 2-4 years that is really low.