FBARC: I/O Asymmetry Aware Buffer Replacement Strategy

Buffer Management is central to database systems; it minimizes the access gap between memory and disk. Primary criterion of most buffer management strategies is hitrate maximization (based on recency, frequency). New storage technologies exhibit characteristics such as read/write asymmetry and low read latency. These have significant impact on the buffer manager: due to asymmetry the cost of page eviction may be several times higher than the cost of fetching a page. Hence buffer management strategies for modern storage technologies must consider write-awareness and spatial locality besides hitrate. In this paper we introduce FBARC a buffer management strategy designed to address I/O asymmetry on Flash devices. FBARC is based on ARC and extends it by a write list utilizing the spatial locality of evicted pages to produce semi-sequential write patterns. FBARC adds an additional list to host dirty pages grouping them into fixed regions called clusters based on their disk location. In comparison to LRU, CFLRU, CFDC, and FOR+, FBARC: (i) addresses write-efficiency and endurance; (ii) offers comparatively high hitrate; (iii) is computationally-efficient and uses static grid-based clustering of the page eviction list; (iv) adapts to workload changes; (v) is scan-resistant. Our experimental evaluation compares FBARC against LRU, CFLRU, CFDC, and FOR+ using trace-driven simulation, based on standard benchmark traces (e.g. TPC-C, TPC-H).