UCSC-SOE-12-10: RAID4S-modthresh: Modifying the Write Selection Algorithm to Classify Medium-Writes as Small-Writes

Michael Sevilla, Rosie Wacha and Scott A. Brandt
07/28/2012 05:24 PM
Computer Science
The goal of this research is to improve the performance of the RAID4S system. For RAID4S, the throughput slope of small-writes, the magnitude of medium sized writes on both sides of the small/large-write selection threshold, and the speedup of small-write performance suggest that medium-writes using the large-write parity calculation will perform better if they use the small-write parity calculation instead. RAID4S-modthresh uses a modified write selection algorithm which only affects medium-writes and keeps the parity calculation and corresponding throughput for small-writes and large-writes intact. RAID4S-modthresh is implemented into the software RAID controller module in the Linux source. Results show a speedup of 2 MB/s for medium-writes without imposing performance or reliability penalties on the rest of the system. This paper also presents other interesting projects for future work in modifying the software RAID controller to improve performance.