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

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.