In storage, there is an inexorable march toward greater capacity. In general this means denser storage. Spinning disks have come up with a variety of ways to skirt the laws of physics to put more bits in a single drive enclosure. Platters were added, drive heads were made more precise, and some companies have tried write schemes like Shingled Magnetic Recording (SMR).
Flash storage has gone through similar iterations to increase density. Chris Evans outlines the challenges and opportunities afforded by quadruple-level cell flash storage.