My first mass storage was a PhiDeck, a tape cassette drive that stored data digitally and that had motors to load and unload the heads and seek. It had a file system, of sorts, that fit in about 6K of RAM. Effective data rate was about 9600 bits/second, and it usually took 20-30 seconds to launch a program.

Primitive and slow as it was, it was still a vast improvement over audio cassettes.

Later, I wrote a software UART and interfaced my Z-80 system to a single Atari 810 disk drive. 96K of storage and tons faster. I got a lot of work done on that system.