> Looking at modern hard disks, I'm unconvinced we could even mass- > produce > something like that today. > > A 40mm radius is comparable to a 3.5" disk, which are generally 5,400- > 7,200 > RPM. 15,000 RPM is the fastest available, but those tend to be low- > capacity and > expensive, and are often 2.5" drives with a huge heatsink.
I am not sure if that hold true. 15K drives have been around at least for 20 years (unless you are considering that part of today?). I was using Seagate Cheetah SCSI drives in 9Gb and 18Gb capacities w/ 3.5" platters spinning at 15K RPM back in the 2000s. They may not be terabyte HDD but 15K RPM was definitely not an issue. -Ali