I've always had a question about those stats. "Drive days" seems a key figure; but 1000 drive days may mean 100 drive with 10 days each, or 10 drives with 100 d

I've always had a question about those stats. "Drive days" seems a key figure; but 1000 drive days may mean 100 drive with 10 days each, or 10 drives with 100 days each. This kind of metric implies that the chance of failing is independent of the age of the drive. Is that so? Was that verified? One of the most failing drives around is the Seagate 4TB, which is a quite old model (it exists since 2013, but it's still sold). How is the drive cohort composed? If it's composed by many old drives and many very new drives, it could mean that we're observing a "mean value" with very little significance. It would be GREAT to have a "long form" CSV with a) drive model b) service start date (or service hours cont) c) failed/not failed during quarter. THAT would help understanding whether drives fail at random or because of old age (and/or what is the correlation between age and failure - there's a threshold effect, or it's linear?)