Also, Commodore also made some 5.25 drives that could store a whole megabyte or more back in the PET days before my time
Indeed - that would be the C= 1001 drive.
I ran a BBS off a Comodore 64 using 2 of these back in the early 80's.
You needed an ieee parallel interface plugged into the cart. port to run it

I remember 'upgrading' the bbs to a 5meg Pet HD -- The thing looked like a metal shoe box with a single led blinking on the front of it..
I still remember the oooohs and aaaaaaah's of my buds.
Cheers.
Siggy.