CSR: Small: Host-Assisted, Software-Defined Solid-State Disk

在过去的二十年里，基于闪存的存储技术已经从一个小众的、相对不为人知的存储技术逐渐发展成为移动和嵌入式媒体的首选，并以固态硬盘（SSD）的形式在笔记本电脑和服务器领域取得了重大进展。越来越多的应用程序使用SSD，趋势表明SSD的使用将显著增长。然而，SSD并不是万能的——实际上，所有商用SSD中的闪存固件都非常严格，并且在输入/输出（I/O）工作负载中高度不适应，这带来了真正的挑战，包括每个SSD的固件成本增加、固件不灵活以及辅助SSD硬件限制。这项工作将解决这些关键问题。该研究将调查ssd应该如何通过软件定义来实现所需的灵活性，以便在各种I/O工作负载中表现最佳。这管理了每个SSD的不灵活固件副本的重复成本，并将当前固件推向更通用和可扩展的软件空间。另一个探索领域是研究如何使ssd能够与主机协作，以便双方的资源可以共享到一个更灵活、性能更高的I/O设备上。这将防止板载SSD辅助硬件被大量过度/不足利用，使主机能够利用特定于工作负载的SSD本身的优化，而不是将数据推回主机。驱动基于闪存的ssd的机制增加了灵活性，这将使系统管理员能够根据使用中的工作负载调整其闪存存储。主机和闪存设备之间增加的合作和透明度应该能够改进应用程序/库/设备级优化，这在当前严格和协议模糊的制度下是不可能的。在主机和SSD之间智能地共享辅助硬件（主要是计算和内存）将允许在给定主机的计算和内存能力的情况下执行更昂贵的SSD优化，并且在给定SSD对底层数据的位置的情况下执行更聪明的I/O优化。此外，将SSD相关的任务带到主机端可以实现应用程序线程和I/O线程的协同优化，从而潜在地改善计算、通信和I/O，同样，SSD任务可以与SSD端的应用程序线程协同优化，从而产生更高效的活动闪存系统。

Over the past two decades flash-based storage has crept up from a niche and relatively unknown storage technology to the mobile and embedded medium of choice, and made significant in-roads in the laptop and server arenas in the incarnation of Solid State Disk (SSD). Increasingly, many applications use SSDs and trends indicate that SSD usage will grow significantly. However, SSDs are no silver bullet - in reality, the flash firmware in all commercial SSDs is very rigid and highly unadaptable across input/output (I/O) workloads creating sincere challenges which include the added cost of firmware per SSD, firmware inflexibility, and assisting SSD hardware limitations. This work will address these key issues. The research will investigate how SSDs should achieve the flexibility they need to perform best for a variety of I/O workloads by being software-defined. This manages the repeating cost of a copy of inflexible firmware for each SSD, and will push the current firmware into the more general and malleable software space. Another area of exploration will be to investigate how SSDs could be made capable of collaborating with the host such that resources on both sides can be shared towards a more flexible and higher-performing I/O device. This will prevent on-board SSD assisting hardware from being vastly over/under utilized, enabling the host to take advantage of workload-specific optimizations on the SSD itself instead of pushing the data back to the host. Increased flexibility in the mechanisms that drive flash-based SSDs will provide system administrators the ability to tune their flash storage for workloads in use. Increased cooperation and transparency between the host and the flash device should enable improved application/library/device-level optimizations that are impossible under the current rigid and protocol-obfuscated regime. Intelligent sharing of assisting hardware (mainly compute and memory) across the host and SSD will enable more expensive SSD optimizations to be performed given the host's compute and memory power, and more clever I/O optimizations to be performed given the SSD's locality to the underlying data. Further, bringing SSD related tasks to the host side can enable co-optimization of application threads and I/O threads, improving potentially computation, communication, and I/O, and similarly, SSD tasks can be co-optimized with application threads on the SSD side, leading to a more efficient active flash system.