The bottom of the memory hierarchy: Semiconductor and DNA data storage

Flash memory is distinct from other types of data storage––such as hard disk drives (HDDs) that are still in active use and floppy disks, CDs, and DVDs that became either extinct or unpopular––in that it is a semiconductor data storage. Smaller, lighter, and lower-power than HDD, flash memory made its first major commercial success as a storage for smartphones and has since made mobile devices truly mobile. It is now a major alternative to HDD even in personal computers, and is penetrating other markets HDD once dominated. Here, we review how flash memory enabled the data-driven world through a sequence of innovations that helped sustain the continued increase of storage capacity, with the highlight being the vertical integration that opened a new era for the memory industry. We will then discuss the emerging cold data storage based on DNA that can lie below flash memory in the memory hierarchy to possibly handle the exploding data. It mimics living organisms that store genetic codes in DNA with unparalleled density and stability. DNA data storage requires the means for high-throughput writing (synthesis). We will review efforts for arrayed DNA synthesis using a highly scalable semiconductor chip. Graphical abstract