SSD Multi-Level Parallel Garbage Collection

Solid-state drives (SSDs) based on NAND flash memory have the advantages of fast access speed, low power consumption and high reliability, have been widely used in storage systems. However, I/O requests from users may be significantly affected by SSD internal garbage collection (GC), and GC operations have always been the core issue limiting SSD performance. In order to solve the problem, this paper proposes a multi-level parallel garbage collection scheme (MP-GC) based on the new SSD flash memory chip architecture. In this scheme, the page-level parallelism and plane-level parallelism of GC operations are realized through the new SSD flash memory chip architecture, the valid pages in the victim block are migrated in parallel, and the victim blocks of multiple planes are reclaimed in parallel. This scheme reduces the time of the GC process and reclaims more invalid pages within a given erasure time. It can also delay future GC operations and effectively reduce the frequency of GC. We extend Flashsim to implement and evaluate our scheme. The experimental results show that compared with the GC scheme based on the traditional SSD flash memory chip architecture, MP-GC reduces the total GC time by 58.2% and the latency by 40% on average.