I barely had time to skim it, but I'm not sure I like how the ST12000NM0008 shows up in the table. I find it really hard to reason about what the real failure rate could end up being on those drives. For example, you've got about 45 days average on each drive, so the failure rate is multiplied by roughly 8 to extrapolate the annualized failure rate. Doesn't that over state the estimated rate of failure since drives will tend to fail more often at the start of their life?

I only guesstimated out of the table and didn't have time to look at the actual data, so it's possible I misread something.