Are Superpages Super-fast? Distilling Flash Blocks to Unify Flash Pages of a Superpage in an SSD

This work discovers a flash memory performance issue resulting from flash superpages organization. Because of process variation, each flash page has its own read/write performance. If a slow page is grouped with a fast page in a superpage unit, computer systems with solid-state drives (SSD) receive a poor performance result. In this work, we prove the existence of this issue by conducting a series of experiments on a real SSD platform. To resolve this issue, we characterize flash memory chips to find hints to organize super-fast superpages in SSDs. By the tips, this work develops a process-variation check scheme (PV Check) that can group a superpage with an optimized performance at runtime with low overheads. According to our experiments, the PV Check scheme has encouraged results in performance improvement. Compared with a traditional method, our work can decrease the extra program and erase latency by 16.61% and 34.55%, respectively.