Flash Saver: Save the Flash-Based Solid State Drives through Deduplication and Delta-encoding

Flash-based SSDs are becoming prevalent in the entire storage stack, but their in-born limitations still remain there, which prevents users´ complete confidence in them, despite of their very attractive performance advantages. One of the critical concerns is their limited lifespan and the associated degrading reliability as the capacity is consumed. A variety of techniques based on caching optimization and redundancy elimination have been proposed to overcome the problem. The main principle behind those techniques is to attempt to reduce the effective write traffic to SSDs. In this paper, we present Flash Saver, which is coupled with the ext2/3 file system and aims to significantly reduce the write traffic to SSDs. Flash Saver deploys deduplication and delta-encoding to reduce the write traffic. Specifically, Flash Saver applies deduplication to file system data blocks and delta-encoding to file system meta-data blocks, based on two important observations which are: (1) There exist large amounts of duplicate data blocks (2) Metadata blocks are accessed/modified much more frequently than data blocks, but with very minimal changes for each update. Our experimental results have shown that Flash Saver can save up to 63% of the total write traffic, which implies reasonably prolonged lifetime, larger effective flash space and higher reliability than that of the original counterpart within their allowable lifespan.