In Winter 1987 I had an Amstrad PC1640HDMD with a 20MB MFM hard disk. I opened the case many times, the disk was just a 5.25 inch device, certainly not like 20 small refrigerators, or even one.

Bonus: I got an RLL controller and turned it into a 30MB hard disk! Couldn't believe it. But getting the interleaving right was time consuming..