弹性RAID：当RAID满足具有内置的透明压缩的SSD时
Elastic RAID: When RAID Meets SSDs with Built-in Transparent Compression
摘要：
本文研究了独立磁盘冗余阵列（RAID）如何充分利用现代固态硬盘（SSD）的内置的【形】透明压缩。在当前实践中，RAID用户被迫选择特定RAID级别（例如，RAID 10或RAID 5），具有固定的存储成本与速度性能之间的权衡。商业市场正在见证新的SSD系列的出现，这些SSD可以在每个4KB LBA（逻辑块地址）块上内部执行基于硬件的无损压缩，对主机操作系统和用户应用程序透明。除了直接降低RAID存储成本外，这种现代SSD还可以使RAID用户免于陷入固定存储成本与速度性能的权衡之中。关键的想法很简单：RAID系统适时地利用高于预期的运行时用户数据可压缩性，以实现动态RAID级别转换，从而在不损害有效存储容量的情况下提高速度性能。本文介绍了设计技术，使和优化这种弹性RAID系统的实际实施。为了演示的目的，我们实现了一个基于Linux软件的弹性RAID原型，支持RAID 5和RAID 10之间的动态转换。与基本的基于软件的RAID 5相比，在足够的运行时数据压缩率（允许超过60%的用户数据从RAID 5转换为RAID 10）下，弹性RAID可以将4KB随机写入IOPS（每秒IO）提高42%，并且在降级模式下将4KB随机读取IOPS提高46%，同时保持相同的有效存储容量。
英文摘要：
This paper studies how RAID (redundant array of independent disks) could take full advantage of modern SSDs (solid-state drives) with built-in transparent compression. In current practice, RAID users are forced to choose a specific RAID level (e.g., RAID 10 or RAID 5) with a fixed storage cost vs. speed performance trade-off. Commercial market is witnessing the emergence of a new family of SSDs that can internally perform hardware-based lossless compression on each 4KB LBA (logical block address) block, transparent to host OS and user applications. Beyond straightforwardly reducing the RAID storage cost, such modern SSDs make it possible to relieve RAID users from being locked into a fixed storage cost vs. speed performance trade-off. The key idea is simple: RAID systems opportunistically leverage higher-than-expected runtime user data compressibility to enable dynamic RAID level conversion to improve the speed performance without compromising the effective storage capacity. This paper presents design techniques to enable and optimize the practical implementation of such elastic RAID systems. For the purpose of demonstration, we implemented a Linux software-based elastic RAID prototype that supports dynamic conversion between RAID 5 and RAID 10. Compared with a baseline software-based RAID 5, under sufficient runtime data compressibility that enables the conversion from RAID 5 to RAID 10 over 60% user data, the elastic RAID could improve the 4KB random write IOPS (IO per second) by 42% and 4KB random read IOPS in degraded mode by 46%, while maintaining the same effective storage capacity.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
