| Title |
BER-based Hybrid Partitioning Technique for Improving Lifetime and Write Performance of High-density NAND Flash SSD |
| Authors |
최기재(Gi Jae Choi) ; 김정훈(Jeong Hun Kim) ; 한태희(Tae Hee Han) |
| DOI |
https://doi.org/10.5573/ieie.2022.59.12.48 |
| Keywords |
NAND flash memory; Hybrid SSD; Bit error rate; Wear leveling; Hot/cold data |
| Abstract |
NAND flash-based solid-state drive (SSD) has a significant challenge in the transition from the triple-level cell (TLC) to quad-level cell (QLC) due to endurance problems caused by the limited number of program/erase cycles. To overcome the endurance problem at the flash translation layer (FTL) level, it is crucial to predict the lifetime of the block to prevent bad blocks, and bit error rate (BER) is used to indicate the lifetime. However, hybrid SSD that uses part of multi-level cell (MLC, TLC, QLC) NAND flash to single-level cell (SLC) mode still selects SLC region based on P/E cycle, so it is not practical due to the high possibility of discrepancy with actual SSD lifetime. This paper proposes a BDQS (BER Disparity based QLC to SLC mode programming) technique that uses BER as endurance for hybrid SSD partitioning. QLC blocks with the same level of BER are selected and converted into SLC regions. The BER of the additionally converted SLC region block is further subdivided to be used as cold data write buffer and hot data storage to improve lifetime. The BDQS technique shows a decrease in capacity by about 9.6% compared to the existing hybrid SSD architecture without the SLC write buffer but prolongs the first bad block time up to 69.0% and system lifetime up to 40.3%, and the average write response time is improved up to 22.0% when compared with baseline. |