Hey my old Radio Shack TRS-80 Model II (the big one, then) kept its entire system on a 512K (not meg.) 8 inch floppy that used only one side. Thanks to 80_Micro magazine and the users who contributed articles & program listings, we soon learned that by punching one extra hole in the floppy (for the optical device that senses the disk) we were able to flip all of them over and use the other sides thus increasing the capacity to an unheard of megabyte total. The whole TRSDOS operating system fit into the bottom of 64K of memory while the so-called video paged in when needed fro &HF000 to the top. We could use that space for anything that wasn't video just fine.
My favorite for storage efficiency was the TI-99-4A (Texas Instruments) that allowed any audio recorder to saave data to. This enabled me to write huge files to my reel-to-reel machine. Even with such a Rube Goldberg rig, it never lost a byte.