Buffer-Aware Garbage Collection for NAND Flash Memory-Based Storage Systems

With continuing improvements in both the price and the capacity, flash memory-based storage devices are becoming a viable solution for satisfying high-performance storage demands of desktop systems as well as mobile embedded systems. Because of the erase-before-write characteristic of flash memory, a flash memorybased storage system requires a garbage collection, which often introduces large performance degradation due to a large number of page migrations and block erase operations. In order to improve the overall I/O performance of the flash-based storage systems, therefore, it is important to support the garbage collection efficiently. In this paper, we propose a novel garbage collection scheme, called buffer-aware garbage collection (BA-GC), for flash memory-based storage systems. In implementing two main steps of the garbage collection module, the block merge step and the victim block selection step, the proposed BA-GC scheme takes into account the contents of a buffer cache (e.g., a page cache and a disk buffer) which is used to enhance the I/O performance of storage systems. The buffer-aware block merge (BA-BM) scheme reduces the number of unnecessary page migrations by enforcing a dirty page eviction in the buffer cache during the garbage collection. The bufferaware victim block selection (BA-VBS) scheme, on the other hand, selects a victim block so that the overall I/O performance can be maximized. Our experimental results show that the proposed BAGC technique improves the overall I/O performance up to 45% over existing buffer-unaware schemes.