What harddrive brands and models do the hyperscalers like Azure use?

It amuses me that the enterprise models are frequently less expensive than "prosumer" and NAS models. It's been a running gag for the last year on ArsTechnica that Seagate's Exos drives are frequently $150 or more cheaper than the alternatives -- each month they have to bring up excuses (another 3db of noise, another 2W of power) as to why you should look at any other drive.

The consumer who wants a 14TB drive is a freak, so the "prosumer" drives are produced in small quantities. It doesn't help at all that these are fragmented into different SKUs for specialized uses. I wouldn't even trust that these are made in large enough volumes to justify testing the firmware. The mass market now is data centers and clouds.

I expect that anyone who can tell you is under NDA. However, I would not expect that they use any brand in particular. Like sticks of RAM, HDDs are fungible to a degree - so long as they meet a certain specification set by the provider, the primary differentiating factors would be failure rate and price, both of which will fluctuate over time.

At this scale, it's also possible that there could be a custom specification but this then locks them into a specific vendor or set of vendors and I'm not sure what could be worth backing themselves into a corner like that.

Backblaze publishes some great reports on hard drive reliability that may be of interest.