DiskSeen: Exploiting Disk Layout and Access History to Enhance I/O Prefetch

Current disk prefetch policies in major operating systems track access patterns at the level of the file abstraction. While this is useful for exploiting application-level access patterns, file-level prefetching cannot realize the full performance improvements achievable by prefetching. There are two reasons for this. First, certain prefetch opportunities can only be detected by knowing the data layout on disk, such as the contiguous layout of file metadata or data from multiple files. Second, non-sequential access of disk data (requiring disk head movement) is much slower than sequential access, and the penalty for mis-prefetching a ‘random’ block, relative to that of a sequential block, is correspondingly more costly. To overcome the inherent limitations of prefetching at the logical file level, we propose to perform prefetching directly at the level of disk layout, and in a portable way. Our technique, called DiskSeen, is intended to be supplementary to, and to work synerg...

• Type: Conference
• Year: 2007
• Where: USENIX
• Authors: Xiaoning Ding, Song Jiang, Feng Chen, Kei Davis, Xiaodong Zhang
• Keywords: Access Patterns, Disk Head Movement, Disk Prefetch Policies, Operating System, USENIX 2007