On the Endurance of the d-Choices Garbage Collection Algorithm for Flash-Based SSDs

摘要

Garbage collection (GC) algorithms for flash-based solid-state drives (SSDs) have a profound impact on its performance and many studies have focused on assessing the so-called write amplification of various GC algorithms. In this article, we consider the family of d-choices GC algorithms and study (a) the extent in which these algorithms induce unequal wear and (b) the manner in which they affect the lifetime of the drive. For this purpose, we introduce two performance measures: PE fairness and SSD endurance. We study the impact of the d-choices GC algorithm on both these measures under different workloads (uniform, synthetic and trace-based) when combined with two different write modes. Numerical results show that the more complex of the two write modes, which requires hot/cold data identification, may not necessarily give rise to a significantly better SSD endurance. Further, the d-choices GC algorithm is often shown to strike a good balance between garbage collection and wear leveling for small d values (e.g., d = 10), yielding high endurance.