A Locality-Preserving Write Buffer Design for Page-Mapping Multichannel SSDs

Advanced SSDs employ a RAM-based write buffer to improve their write performance. The buffer intentionally delays write requests in order to reduce flash write traffic and reorders them to minimize the cost of garbage collection. This work presents a novel buffer algorithm for page-mapping multichannel SSDs. We propose grouping temporally or spatially correlated buffer pages and writing these grouped buffer pages to the same flash block. This strategy dramatically increases the probability of bulk data invalidations in flash blocks. In multichannel architectures, channels are assigned to their own groups of buffer pages for writing, and so channel striping does not divide a group of correlated buffer pages into small pieces. We have conducted simulations and experiments using a SSD simulator and a real SSD platform, respectively. Our results show that our design greatly outperforms existing buffer algorithms.