Bargain Cache: Using File-System Metadata to Reduce the Cache Miss Penalty

Current cache replacement policies mostly work at the block device level. Block level policies try to achieve better hit ratio by balancing the frequently and recently visited pages, however, further improvements can be realized by using file-system metadata. There are two reasons for this. First, sequential access of disk data is more quickly than non-sequential access, that is to say, the cache penalty of sequential blocks miss can be significantly lower than that of random blocks miss. Second, in most storage systems, files are stored and accessed sequentially. We notice this and propose a novel cache management policy, called bargain cache, which prefers to drop sequential pages by using the file-system metadata, so that hard disks could work under sequential access mode as much as possible. Simulation results show that our technique can efficiently reduce the cache miss penalty, thus improve the overall caching performance.