I don't think the HDDs are being used for any intensive loads. They have too much latency for most of that. It's probably just archival storage for their scraped content and generated slop.
I don't mean that type of archive, but rather "just in case" data like "last month's scrape of this website" after we scraped it 5 more times this month or higher resolution versions of book scans. You might want to still be able to dump it out quickly if you need it. Money is no object for these companies and the cost of HDDs is more than low enough for the flexibility they provide.
zozbot234|13 days ago
digiown|13 days ago
pixl97|13 days ago