Disks form the central element of Cloud-based storage, whose demand far outpaces the considerable rate of innovation in disks. Exponential growth in demand, already in progress for 15+ years, implies that most future disks will be in data centers and thus part of a large collection of disks. We describe the “collection view” of disks and how it and the focus on tail latency, driven by live services, place new and different requirements on disks. Beyond defining key metrics for data-center disks, we explore a range of new physical design options and changes to firmware that could improve these metrics.
We hope this is the beginning of a new era of “data center” disks and a new broad and open discussion about how to evolve disks for data centers. The ideas presented here provide some guidance and some options, but we believe the best solutions will come from the combined efforts of industry, academia and other large customers.