WLFC: Write Less in the Flash-based Cache Chaos Dong Fang Wang Jianshun Zhang Huazhong University of Huazhong University of Huazhong University of Science and Technology Science and Technology Science and Technology Huhan, China Huhan, China Huhan, China Email:
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[email protected] Abstract—Flash-based disk caches, for example Bcache [1] and log-on-log [5]. At the same time, the Open-Channel SSD Flashcache [2], has gained tremendous popularity in industry (OCSSD) has became increasingly popular in academia. in the last decade because of its low energy consumption, non- Through a standard OCSSD interface, the behaviors of the volatile nature and high I/O speed. But these cache systems have a worse write performance than the read performance because flash memory can be managed by the host to improve the of the asymmetric I/O costs and the the internal GC mechanism. utilization of the storage. In addition to the performance issues, since the NAND flash is In this paper, we mainly make three contributions to optimize a type of EEPROM device, the lifespan is also limited by the write performance of the flash-based disk cache. First, we Program/Erase (P/E) cycles. So how to improve the performance designed a write-friendly flash-based disk cache system and the lifespan of flash-based caches in write-intensive scenarios has always been a hot issue. Benefiting from Open-Channel SSDs upon Open-Channel SSDs, named WLFC (Write Less in (OCSSDs) [3], we propose a write-friendly flash-based disk cache the Flash-based Cache), in which the requests is handled system, which is called WLFC (Write Less in the Flash-based by a strictly sequential writing method to reduce write Cache).