PR-SSD: Maximizing Partial Read Potential by Exploiting Compression and Channel-Level Parallelism

Abstract

Recent NAND flash memories provide a partial read operation that can read a page partially and has lower latency than a normal read operation. In order to maximize the benefit of the partial read operation, compression techniques can be applied to improve performance by generating additional partial page requests via compressing pages into smaller ones. Unfortunately, existing compression-support SSDs suffer from a huge decompression latency that eventually cancels the benefit of the partial read operation. In this paper, we propose Partial Read-aware SSD (PR-SSD) for fully exploiting partial read operations. In order to mitigate the decompression latency, we propose a new compression algorithm, called Dominant Pattern Compression (DPC), which has extremely low decompression latency. Because uncompressed page requests cannot exploit the partial read operation, we propose split Flash Translation Layer (FTL) that can split the requests into smaller ones and allocate them to different channels for exploiting channel-level parallelism in SSD. Experimental results reveal that PR-SSD can reduce the read response time by 18% on average and also the number of writes and write response time by 29% and 24% on average, respectively.