WOLF-A Novel Reordering Write Buffer to Boost the Performance of Log-Structured File Systems

Jun Wang and Yiming Hu
Department of Electrical & Computer Engineering and Computer Science
University of Cincinnati
Cincinnati, OH 45221-0030
e-mail: {wangjun, yhu}@ececs.uc.edu

Abstract:

This paper presents the design, simulation and performance evaluation of a novel reordering write buffer for Log-structured File Systems (LFS). While LFS provides good write performance for small files, its biggest problem is the high overhead from cleaning. Previous research concentrated on improving the cleaner's efficiency after files are written to the disk. We propose a new method that reduces the amount of work the cleaner has to do before the data reaches the disk. Our design sorts active and inactive data in memory into different segment buffers and then writes them to different disk segments. This approach forces data on the disk into a bimodal distribution. Most data in active segments are quickly invalidated, while inactive segments are mostly intact. Simulation results based on both real-world and synthetic traces show that such a reordering write buffer dramatically reduces the cleaning overhead, slashing the system's overall write cost by up to 53%.