Average seek time across a disk which is much larger physically than the disks in use today.
It wasn't rare at all to find fair sized servos (as opposed to steppers in consumer grade stuff in the 80's) in those old disk pack units (the size of a washing machine).
You can't really compare 'common 7200 RPM drives' of today with a top-of-the-line medium from the 70's, physics didn't change at all in that time. That's why there are 'servo tracks' on the drive, they help with finding the right track (in a stepper scenario you don't actually need those, the stepper resolution defines where the tracks are).
Today enterprise level drives achieve < 4 ms average seek times at a price point which is a small fraction of what that drive cost in the 70's.
That's where the real improvement factor sits: performance (both in capacity, seek time and transfer rates) vs cost.
Well, physics didn't change, but our understanding of it did. Modern read heads are based on the giant magnetoresistive effect which was only discovered in 1988. It's actually one of the fastest transitions from fundamental physics discovery to wide use (GMR read heads were widely used from 2001-2002 or so)
The actual mass of the heads and arms was an issue as well; you had to be careful not to seek back and forth at the natural resonance frequency of the cabinet or the "washing machines" would start walking across the floor.
It wasn't rare at all to find fair sized servos (as opposed to steppers in consumer grade stuff in the 80's) in those old disk pack units (the size of a washing machine).
You can't really compare 'common 7200 RPM drives' of today with a top-of-the-line medium from the 70's, physics didn't change at all in that time. That's why there are 'servo tracks' on the drive, they help with finding the right track (in a stepper scenario you don't actually need those, the stepper resolution defines where the tracks are).
Today enterprise level drives achieve < 4 ms average seek times at a price point which is a small fraction of what that drive cost in the 70's.
That's where the real improvement factor sits: performance (both in capacity, seek time and transfer rates) vs cost.
And that's many orders of magnitude.