CSR:Small: Efficient FTL Buffer Management for High-Performance Solid State Drives

在过去的几十年里，磁盘的访问时间每年提高约8%，而处理器速度每年提高60%。磁盘和处理器之间的巨大性能差距意味着许多大型应用程序受到底层存储系统性能的限制。闪速存储器是一种新兴的存储技术，它显示出巨大的前景，以弥补基于磁盘的存储设备的局限性。基于闪存的存储的一个关键优势是其读写性能比磁盘好得多。基于闪存的存储（如固态驱动器）提供对设备所有区域的快速随机访问。另一方面，对闪存的写入比读取慢得多。此外，除非使用干净的块，否则写入闪存之前必须进行擦除，并且擦除周期的数量是有限的。为了克服这些缺点，闪存转换层（FTL）被设计为提供逻辑地址到物理地址之间的动态地址映射、损耗均衡、垃圾收集和缓冲区缓存。FTL中的一个小内存缓冲区用于执行这些功能。 本项目将重点研究使用最少内存缓冲区来实现高性能和低能耗的技术。研究任务包括有效的冷热数据分类算法，以及如何减少磨损均衡和垃圾收集的内存需求。这项工作将提高对闪存的基本理解，并将扩展闪存的能力，以支持许多关键应用。

In the past several decades, the access time of magnetic disks has improved about 8% per year while processor speeds have improved at an astounding 60% per year. The tremendous performance disparity between disks and processors means that many large-scale applications are limited by the performance of the underlying storage systems. Flash memory is an emerging storage technology that shows tremendous promise to compensate for the limitations of magnetic disk-based storage devices. A key advantage of flash-based storage is that its read-write performance is much better than disk. Flash memory-based storage like solid state drives provides fast random access to all areas of the device. On the other hand, writes to flash memory are much slower than reads. Furthermore, writes to flash must be preceded by an erase unless a clean block is used, and the number of erase cycles is limited. To overcome these drawbacks, a Flash Translation Layer (FTL) is designed to provide dynamic address mapping between logical addresses to physical addresses, wear-leveling, garbage collection, and buffer caching. A small memory buffer in FTL is used to perform these functions. This project will focus on techniques to use the least amount of memory buffer to achieve high performance and low energy consumption. The research tasks include efficient heuristics for hot and cold data classification and how to reduce memory requirement for wear-leveling and garbage collection. This effort will improve the fundamental understanding of flash memory and will extend the capability of flash memory to support many critical applications.