They also know about mixing brands/batches/etc. to avoid exactly this kind of correlated failure. During one of my oncalls, we had an uncomfortably large number

They also know about mixing brands/batches/etc. to avoid exactly this kind of correlated failure. During one of my oncalls, we had an uncomfortably large number of failures fitting this kind of pattern, but they were well enough distributed and we had enough data redundancy that there was no data loss. Sometimes there's safety in numbers, if you know how to make those numbers work for you rather than against you.