Algorithms, Performance

We design and implement FD-Buffer, a buffer manager for database systems running on flash-based disks. Unlike magnetic disks, flash media has an inherent read-write asymmetry: writes involve expen-sive erase operations and as a result are usually much slower than reads. Therefore, we address this asymmetry in FD-Buffer. Specifi-cally, we use the average I/O cost per page access as opposed to the traditional miss rate as the performance metric for a buffer. We de-velop a new replacement policy in which we separate clean and dirty pages into two pools. The size ratio of the two pools is automati-cally adapted to the read-write asymmetry and the runtime work-load. We evaluate FD-Buffer with trace-driven experiments on real flash disks. Our evaluation results show that our algorithm achieves up to 33 % improvement on the overall performance on commod-ity flash disks, in comparison with the state-of-the-art flash-aware replacement policy