A Novel NAND Flash Memory Architecture for Maximally Exploiting Plane-Level Parallelism

Solid-state drive (SSD) has become one of the most dominant storage devices and is rapidly replacing conventional storage devices. The core component of SSD is NAND flash memory (NFM), where the actual data are stored. Cost pressure is the most critical factor limiting the further deployment of SSDs and past researches have focused on developing cost-effective high-density NFM. Although the cost-driven technology development increases per-chip capacity, it reduces channel-/way-level parallelisms for the given device capacity, resulting in the performance degradation. Such observation directs us to focus on a novel NFM architecture exploiting plane-level parallelism. The distinct features of this architecture are: 1) enabling a decoupled word-line (WL) selection for the mated planes and 2) segmenting each plane into subplanes for further maximizing the plane-level parallelism. The experimental results show that decoupled WL selection improves the throughput by up to 21.3% with a marginal overhead of less than 1%, compared to the conventional NFM architecture. In addition, adopting the plane segmentation improves the throughput by up to 43.9% with an additional overhead of 14%. Considering the tradeoff between performance and overhead, the proposed NFM architecture is a cost-efficient method to secure high performance under decreasing channel-/way-level parallelisms in high-density NFM.