Yeah my experience in the past was that datacenter hardware (air cooled, at least, I've never dealt with water cooled) uses tiny fans at or about 15000RPM, so it matches basically what you're saying or worse.

I always loved this video: https://www.youtube.com/watch?v=tDacjrSCeq4

That was one of those fantastic early google videos/youtube things I probably watched 100 times. This was another from (roughly) that era: https://www.youtube.com/watch?v=ULSA5wktywI