  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.
