I would think you'd also want to be hedging your bets a bit against some kind of catastrophic bug. Flexibility in your supply lines has also got to be a big plus (and help smooth sailing with various disasters)

Yev here -> Yes we want to mitigate large batch failures by adding some drive/vendor diversification, that's definitely part of the equation!

Do you have an algorithm of sorts that takes into account price and historical failure rate by drive model and gives you an easy "yea or nay" for purchase decisions? Seems like you might be able to automate drive purchases with such a system (similar to limit orders on financial securities).

Yev here -> It's less of an algorithm and more of a purchasing department with lots of spreadsheets that tie into the AFR data as a data point - but yes, it's possible we could automate it, but there's some factors that our supply-chain team would need to be involved in anyway (like vendor diversity, no large batches of single drives etc...) that make outputting that algorithm a bit harder.

I was wondering this as well, it seems pretty easy to write.

Also, if you don't use one, please elaborate if you can why the obvious MTBF delta projection idea is bunk. I'm sure your talented team has thoroughly thought through all of this