Solid State Drives (SSDs)

Abstract

Solid-state drives (SSDs) are unanimously considered the enabling factor for bringing enterprise storage performances to the next level. Indeed, the rotating-storage technology of Hard Disk Drives (HDDs) can’t achieve the access-time required by applications where response time is the critical factor. On the contrary, SSDs are based on solid state memories, namely NAND Flash memories: in this case, there aren’t any mechanical parts and random access to stored data can be much faster, thus addressing the above mentioned needs. In many applications though, the interface between host processors and drives remains the performance bottleneck. This is why SSD’s interface has evolved from legacy storage interfaces, such as SAS and SATA, to PCIe, which enables a direct connection of the SSD to the host processor. In this chapter we give an overview of the SSD’s architecture by describing the basic building blocks, such as the Flash controller, the Flash File System (FFS), and the most popular I/O interfaces (SAS, SATA and PCIe).