SetMP: Set Associative Mapping Management for Multi-plane Optimization in SSDs

Modern solid state drives (SSDs) are composed of a four-level parallel structure, including channels, chips, dies, and planes, to enhance SSD performance with maximum access parallelism. Because the planes within the same die share the same set of control units and peripheral circuits, it generally has to open multiple aligned blocks to enable access parallelism through multi-plane (MP) operations. Such a passive method, however, cannot effectively exploit plane level parallelism, since MP operations can only be triggered when the accessed data pages have the same offset address across the planes. In addition, it will worsen the block open time issue, as multiple aligned blocks are opened to enable MP operations for simultaneous data writing. This, in turn, increases the error rate when reading data from blocks with long open time. This paper introduces SetMP, a novel approach that proactively aggregates requests to exploit plane level parallelism through set associative management. By increasing the frequency of MP operations, SetMP enhances I/O responsiveness while reducing the open time of block associated with maintaining multiple open blocks for MP operations. Evaluation results demonstrate that SetMP achieves an average reduction in I/O latency of 16.9%, without significantly increasing the open time of block, outperforming existing optimization schemes.