Thanks for the information/lesson. I honestly enjoyed reading it.
You're welcome. I developed a disk driver many years ago, and always marvel at how far we have come in 3 decades. The magnitude of the numbers have changed, but the mechanical limitations are still the same.
To give you an idea of how much has changed, consider a typical consumer disk drive today: either a 3-1/2 inch desktop drive or a 2-1/2 inch laptop drive. The drive has its own cache and the drive controller circuitry built in. You can buy a moderate size drive for under $100, and hold it in one hand.
Back when I was doing disk driver development, the disk alone was about the size of a dishwasher. The disk controller (for up to 8 disks) was the size of a small kitchen refrigerator. And the cache memory was the size of a minivan (disk cache memory was rare in those days, though).
It isn't just disk storage technology that has advanced so far. Back then, a "scientific" mainframe was distinguished from a "data processing" mainframe by its ability to do floating point operations more quickly. If you were to run the same benchmarks on today's computers, you'd find that your iPhone is 20-50 times faster than the top-of-the-line scientific mainframes back then.