wearMeter: an Accurate Wear Metric for NAND Flash Memory

The program/erase (P/E) cycle is frequently utilized as a yardstick for indicating the wear degree of flash memory. However, this metric exhibits a significant limitation in accuracy. After enduring the same number of P/E cycles, the wear degree of flash memory could vary due to factors such as ambient temperatures and dwell time between two P/E cycles. To reflect the true wear degree of flash memory, this paper proposes an accurate and consistent metric, wearMeter. The proposed metric, independent of wear sources, guarantees accurate offline wear measurement. Moreover, by comparing to the error-correcting capability of the ECC engine, it offers a straightforward assessment of block remaining reliability margins. Leveraging wearMeter, this paper further proposes a novel low-wear Single-Level Cell (SLC) mode, lSLC, which significantly reduces wear compared to the default SLC mode. Experiments show that lSLC demonstrates over 3X the P/E cycles of the default SLC mode under the same conditions, without performance losses.