BAGC: Buffer-Aware Garbage Collection for Flash-Based Storage Systems

NAND flash-based storage device is becoming a viable storage solution for mobile and desktop systems. Because of the erase-before-write nature, flash-based storage devices require garbage collection that causes significant performance degradation, incurring a large number of page migrations and block erasures. To improve I/O performance, therefore, it is important to develop an efficient garbage collection algorithm. In this paper, we propose a novel garbage collection technique, called buffer-aware garbage collection (BAGC), for flash-based storage devices. The BAGC improves the efficiency of two main steps of garbage collection, a block merge step and a victim block selection step, by taking account of the contents of a buffer cache, which is typically used to enhance I/O performance. The buffer-aware block merge (BABM) scheme eliminates unnecessary page migrations by evicting dirty data from a buffer cache during a block merge step. The buffer-aware victim block selection (BAVBS) scheme, on the other hand, selects a victim block so that the benefit of the buffer-aware block merge is maximized. Our experimental results show that BAGC improves I/O performance by up to 43 percent over existing buffer-unaware schemes for various benchmarks.