SSD Architecture and PCI Express Interface
Flash-memory-based solid-state disks (SSDs) provide faster random access and data transfer rates than electromechanical drives and today can often serve as rotating-disk replacements, but the host interface to SSDs remains a performance bottleneck. PCI Ex
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SSD Architecture and PCI Express Interface K. Eshghi and R. Micheloni
Abstract Flash-memory-based solid-state disks (SSDs) provide faster random access and data transfer rates than electromechanical drives and today can often serve as rotating-disk replacements, but the host interface to SSDs remains a performance bottleneck. PCI Express (PCIe)-based SSDs together with an emerging standard called NVMe (Non-Volatile Memory express) promises to solve the interface bottleneck. This chapter walks the reader through the SSD block diagram, from the NAND memory to the Flash controller (including wear leveling, bad block management, and garbage collection). PCIe basics and different PCIe SSD architectures are reviewed. Finally, an overview on the standardization effort around PCI Express is presented.
2.1 Introduction Creativity is just connecting things. When you ask creative people how they did something, they feel a little guilty because they didn’t really do it, they just saw something. It seemed obvious to them after a while. – Steve Jobs
Solid-state drives promise to greatly enhance enterprise storage performance. While electromechanical disk drives have continuously ramped in capacity, the rotatingstorage technology doesn’t provide the access-time or transfer-rate performance required in demanding enterprise applications, including on-line transaction processing, data mining, and cloud computing. Client applications are also in need of
K. Eshghi () • R. Micheloni Enterprise Computing Division, Integrated Device Technology, Inc., San Jose, CA, USA e-mail: [email protected]; [email protected] R. Micheloni et al., Inside Solid State Drives (SSDs), Springer Series in Advanced Microelectronics 37, DOI 10.1007/978-94-007-5146-0 2, © Springer ScienceCBusiness Media Dordrecht 2013
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K. Eshghi and R. Micheloni
an alternative to electromechanical disk drives that can deliver faster response times, use less power, and fit in smaller mobile form factors. Flash-memory-based Solid-State Disks (SSDs) can offer much faster random access to data and faster transfer rates. Moreover, SSD capacity is now at the point that the drives can serve as rotating-disk replacements. But for many applications the host interface to SSDs remains a bottleneck to performance. PCI Express (PCIe)-based SSDs together with emerging host control interface standards address this interface bottleneck. SSDs with legacy storage interfaces are proving useful, and PCIe SSDs will further increase performance and improve responsiveness by connecting directly to the host processor.
2.2 SSD Architecture Flash cards, USB keys and Solid State Disks are definitely the most known examples of electronic systems based on non-volatile memories, especially of NAND type (Sect. 2.4). Several types of memory cards (CF, SD, MMC, : : :) are available in the market [1–3], with different user interfaces and form factors, depending on the needs of the target application: e.g. mobile phones need very small-sized removable media like SD. SSDs are the e
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