> Correlated failures are common in drives.
This is why, when I was building DIY arrays for startups (around the same time Backblaze published their first pod design [1]), I went through the extra effort of sourcing disks from as many different vendors as possible.
Although it was somewhat more time consuming and limited how good a price I could get and how fast the delivery could be, it meant that, for any given disk drive size, it meant I could build an array as large as 12 where no 2 drives were identical in model and manufacturing batch [2].
Of course, it's still a vanishingly rare risk, and "nobody" cares about hardware any more. It does help to remember, at least once in a while, that, on some level, cloud computing really is "someone else's servers" and to hope that someone else still maintains this expertise.
[1] though I used SuperMicro SAS expander backplane chasses for performance reasons
[2] and firmware from the factory, although this is somewhat irrelevant, as one can explicitly load specific firmware versions, and, IIRC, the advantages of consistent firmware across drives, behind a hardware RAID card, outweighed the disadvantages