R&D: Efficient Caching on Parity Chunks in RAID-Enabled SSDs

IEICE Electronics Express has published an article written by Zhigang Cai, Lihao Song, College of Computer and Information Science, Southwest University of China, and Xiaoning Peng, The College of Computer Science and Engineering, Huaihua University.

Abstract: “Caching the updated parity chunks in the RAID buffer can absorb update operations on parity chunks of data stripes in RAID-enable SSDs. Thus, the negative effects of write penalty can be minimized. However, caching integrated parity chunks fails to efficiently use the capacity-limited RAID buffer, as sometimes a major parts of parity chunk are not modified comparing with the parity chunk saved in SSD blocks. This paper presents a patch-based cache management scheme on parity chunks, for improving cache use efficiency of RAID-enabled SSDs. Specifically, it only caches the modified portions of parity chunks in the buffer(called parity patches), which are corresponding to the updated parts of data chunks in the same stripe. Through a series of simulation tests on several disk traces, we illustrate our proposal can noticeably reduce the I/O latency by between 12.2% and 17.1% and the number of block erases by 20.8% on average, in contrast to state-of-the-art approaches. In brief, our proposed cache management scheme can work in RAID-enabled SSDs to achieve better I/O performance and extend the lifespan of SSDs.“