An Efficient Block Address Transformation Scheme in Block Layer for Flash-Based SSDs

Abstract

Flash-based solid state drives (SSDs) are widely adopted in both industry and the academia since SSDs offer higher performance, lower latency, and lower power consumption compared with traditional hard disk drives (HDDs). Unfortunately, the performance of SSDs can be affected by I/O access patterns. For example, random I/O operation degrades the SSD performance compared with sequential I/O operation since the random I/O operation reduces the spatial locality and increases garbage collection (GC) overhead. To handle this issue, in this article, we propose an efficient block address transformation scheme in the block layer to improve both performance and portability. To do this, we first transform random access patterns to sequential access patterns by sequentializing the block addresses in the block layer. Second, we devise a mapping table for managing transformed block addresses. Third, we support correct read operations and transaction processing for updating the mapping table to avoid sacrificing the consistency. Finally, we provide a cleaning scheme to reclaim invalid data generated by the transformed sequential access. This scheme increases spatial locality, reduces GC overhead, and operates well on any file systems or devices. Experimental results show the proposed scheme improves performance by up to 2x, 1.86x, 2.15x, and 42.8% compared with existing scheme in the case of diverse file systems such as EXT4, XFS, BTRFS, and F2FS, respectively.

Keywords

• Flash-based SSDs
• block layer
• I/O performance
• garbage collection