I’ve been referring to the disk (rotation) speed bottleneck for years, but I don’t really have a clean link for it. Let me fix that right now.
The first hard disks ever were introduced by IBM in 1956. They rotated 1,200 times per minute. Today’s state-of-the-art disk drives rotate 15,000 times per minute. That’s a 12.5-fold improvement since the first term of the Eisenhower Administration. (I understand that the reason for this slow improvement is aerodynamic — a disk that spins too fast literally flies off the spindle.)
Unfortunately, random seek time is bounded below, on average, by 1/2 of a disk’s rotation time. Hence disk seek times can never get below 2 milliseconds.
15,000 RPM = 250 rotations/second, which implies 4 milliseconds/rotation.
From that, much about modern analytic DBMS design follows.