SWEEP: Gathering Hot Read/Write Data Together to Minimize Read Reclaims in SSDs

Read disturb is a circuit-level noise in high-density solid-state drives (SSDs), which may corrupt existing data in SSD blocks and then cause high read error rates. The approach of read reclaim (RR) is commonly used to avoid read disturb errors by migrating the valid data pages to other free blocks for resetting negative effects of read disturbs, but it affects both I/O responsiveness and SSD lifetime. This paper proposes SWEEP to minimize the number of RR operations. Specifically, it gathers hot read and hot write data pages together, and saves them in a portion of designated blocks. After that, the hot write data pages will be invalidated and the hot read data pages in such blocks are likely to be migrated to other blocks through garbage collection (GC). Consequently, the read disturbs on these hot read data pages will be reset, without additional RR operations. Trace-driven simulation experiments show that our proposal can significantly reduce the number of RR operations by between 1.6 % and 74.4 %, which contributes to a maximum reduction of 29.7 % on total erase operations, indicating a better lifetime of SSD devices. In addition, it can reduce the overall I/O response time by up to 52.9 %, compared to existing optimization schemes for SSDs.