hesela.devRetention Interference Aware Neighbor-Cell Assisted Correction
ReNAC is a proposed NAND recovery technique that adjusts read thresholds using retention age and vertically adjacent cell states.
After failed correction, neighboring data inform a read-offset model indexed by retention age. This extends neighbor-aware program-interference recovery to retention interference. [1]
The NAC predecessor replaces selected bit positions in a buffered page according to the neighbor state used for each reread, then attempts ECC again. Neighbor-aware sensing is not a single read with a different voltage for every cell. [2]
Relations
Limitations
- Meaningful lifetime improvement was not demonstrated for the tested 3D MLC chips; TLC/QLC benefits remained future work. [1]
- The predecessor study concerns planar MLC program interference; its outcomes do not establish ReNAC retention benefits. [2]
- The Figure 16 comparison excludes ReNAC and uses lifetime estimated from measured error rates and an assumed ECC limit, not a direct SSD lifetime measurement. [1]
Citations
- Luo et al. Improving 3D NAND Flash Memory Lifetime by Tolerating Early Retention Loss and Process Variation. POMACS 2018, sections 6.4-6.5.
- Cai, Yalcin, Mutlu, Haratsch, Unsal, Cristal and Mai. Neighbor-Cell Assisted Error Correction for MLC NAND Flash Memories. SIGMETRICS 2014, sections 6.1-6.3.
Sources & caveats
- Author manuscript, sections 6.4-6.5 and Figure 16. Literature synthesis, not a Hesela experiment.
- NAC mechanism checked against Cai et al. 2014, sections 6.1-6.3; kept separate from ReNAC's 2018 proposal and evaluation limits.