Design Methodology for Highly Reliable, High Performance ReRAM and 3-Bit/Cell MLC NAND Flash Solid-State Storage

This paper proposes design methodology for highly reliable, high performance ReRAM and 3-bit/cell multi-level cell (MLC) NAND flash solid-state storage. Six techniques, calibrated RRef (CR), flexible RRef (FR), adaptive asymmetric coding (AAC), verify trials reduction (VTR), bits/cell optimization (BCO), and balanced RAID-5/6 are proposed. CR, FR, AAC, and VTR are for ReRAM. CR and FR change the read-reference resistance (RRef) to reduce the BER. AAC first increases the population of Set and then Reset. The BER reduction with FR and AAC is 69 and 78% with 60 and 75% asymmetry, respectively. In VTR, by changing the number of acceptable bit-errors, the total Reset time is reduced by 97% at maximum with small ECC calculation overhead. The reliability of 3-bit/cell MLC NAND flash memory is improved by BCO and balanced RAID-5/6. BCO reallocates 3-bit/cell MLC to 2-bit/cell MLC and single-level cell (SLC) and the write/erase cycle increases by over 22-times. Balanced RAID-5/6 evenly allocates upper/middle/lower pages to a stripe to reduce the RAID failure rate by 98%.