Garbage Collection Techniques in Solid-State Drives (SSDs)

The widespread adoption of Solid-State Drives (SSDs) in modern computing is driven by their speed, power efficiency, and reliability over traditional hard disk drives (HDDs). However, SSDs use NAND flash memory, which inherently limits direct overwriting of data, requiring efficient Garbage Collection (GC) processes to manage invalid pages and consolidate valid data. While GC is essential for maintaining SSD performance, it also introduces challenges such as write amplification, increased latency, and uneven wear distribution, all of which can shorten SSD lifespan and degrade reliability. This paper presents a comprehensive classification and evaluation of GC techniques, addressing performance optimization, data placement and victim block selection strategies, emerging SSD architectures, and RAID and AFA GC mechanisms. By examining both state-of-the-art research and practical implementations, it highlights the evolution of GC strategies, from traditional methods to advanced host-assisted and machine learning-driven approaches, offering valuable insights for researchers and industry professionals aiming to optimize SSD performance, lifetime, and efficiency.