Improving SSD Performance Using Adaptive Restricted-Copyback Operations

Copyback operation can improve the performance of data migrations in SSD, but they are rarely used because of their error propagation problem. In this paper, we propose an integrated approach that maximizes the efficiency of copyback operations but does not compromise data reliability. First, we propose a novel per-block error propagation model under consecutive copyback operations. Our model significantly increases the number of successive copybacks by exploiting the aging characteristics of NAND blocks. Second, we devise a resource-efficient error management scheme that can handle successive copybacks where pages move around multiple blocks with different reliability. Experimental results show that the proposed technique can improve the IO throughput by up to 25% over the existing technique.