Flash-based disk cache has been widely used in indurstry in the last decade, such as flashcache (facebook, 2010), bcache (opensource, 2013). These cache systems typically use commercial SSDs to store and manage cache data. However, these flash-based disk cache systems are unfriendly to write-intensive application because of the special physical characteristic of the NAND flash memory. Recently, more and more new storage devices and emulators have come out. Benifiting from these works, the paper introduces a write-friendly flash-based disk cache system, called WLFC (Write Less in Flash-based Cache) which mainly makes three contributions. First is proposing a new flash-based disk cache system by combining the Open channel SSDs with log structure. Second is proposing a new replacement algorithm for OCSSD cache to determine weather the data should be evicted by the unused area size of the data bucket. Third is that WLFC saves as little metadata as possible both to ensure the consistency after power failure and to reduce the overhead of SSD and DRAM. Our experiments show that WLFC can significantly reduce the write latency by 70%, increase the throughput up to 4.5x, and remove 88.9% unnecessary erase operations at most.

中文翻译：

---

WLFC：在基于闪存的缓存中写入较少

基于闪存的磁盘缓存在过去十年中已广泛用于工业中，例如闪存缓存（facebook，2010），bcache（开源，2013）。这些缓存系统通常使用商用SSD来存储和管理缓存数据。但是，由于NAND闪存的特殊物理特性，这些基于闪存的磁盘缓存系统对写密集型应用程序并不友好。最近，越来越多的新存储设备和仿真器问世。从这些工作中获益，本文介绍了一种写友好的基于闪存的磁盘缓存系统，称为WLFC（在基于闪存的缓存中写入更少），它主要做出了三点贡献。首先是通过将开放通道SSD与日志结构结合起来，提出一种新的基于闪存的磁盘缓存系统。其次是为OCSSD缓存提出一种新的替换算法，以确定天气应由数据存储区的未使用区域大小来驱逐数据。第三，WLFC保留了尽可能少的元数据，既可以确保断电后的一致性，又可以减少SSD和DRAM的开销。我们的实验表明，WLFC可以显着减少70％的写入延迟，将吞吐率提高至4.5倍，最多可以消除88.9％的不必要擦除操作。