Remember, disks started out these huge things that had their own room, then shrank down to their own cabinet, then shrank to huge things that only two or three fit in a 19" rack. As time passed disks got smaller until the 5.25" full height form factor that was so impressive in the ST-506 drive from Shugart Technology.
Eventually those disks gave way to 3.5" drives which is pretty much everything today except for Laptop drives that are 2.5" and smaller. (Ya gotta love the IBM Microdrives). Anyway,