High-Density Solid-State Storage: A Long Path to Success

This paper covers the recent evolution of high-density solid-state storage, which is the most prominent storage solution of the 21st century. The attention is focused on the two integrated technologies that more than any other are revolutionizing the storage landscape: the NAND Flash technology and the Phase-Change Memory (PCM) technology. The success of the NAND Flash technology has been the outcome of its strenuous attempt not only to maximize the bit storage density achievable with a cost-effective process over the surface of a silicon die, but also to increase that density at a regular pace thanks to favorable evolutionary approaches. In this way, NAND Flash memories have become the elective storage media for a wide variety of electronic applications, overwhelming hard-disk drives. The PCM technology represents, instead, a notable exploitation of a new memory concept to provide a novel trade-off among cost, performance and reliability. In particular, the PCM attempt to address performance more than cost needs is driving a shift in the traditional storage hierarchy, with storage-class memory finally becoming a reality.