Improve Effective Capacity and Lifetime of Solid State Drives

Flash-based SSDs are becoming increasingly popular in modern storage systems, especially in high-performance computing infrastructures. However, several inherent technical limitations still remain to prevent their widespread deployment. One of the critical concerns is their limited lifetime, which is directly relevant to the total writes experienced by SSDs. In this paper, we present a Content and semantics Aware File System (CSA-FS) which is able to reduce write traffic to SSDs. It employs deduplication and delta-encoding techniques to file system data blocks and semantic blocks, respectively. It is motivated by two important observations: (1) there exists a huge amount of content redundancy within primary storage systems, and (2) semantic blocks are visited much more frequently than data blocks, with each update bringing very minimal changes. By separately deduplicating redundant data blocks and delta-encoding similar semantic blocks, CSA-FS can significantly reduce the total write traffic to SSDs and greatly improve their lifetime correspondingly, at an acceptable cost of at most 7% performance degradation across a variety of workloads.