BER Evaluation System Considering Device Characteristics of TLC and QLC NAND Flash Memories in Hybrid SSDs with Real Storage Workloads

This paper proposes BER evaluation system that evaluates BER of TLC and QLC NAND flash memories with reliability information such as write and erase (W/E) cycle and data-retention time by combining SSD model emulator and device characteristics of NAND flash memories. Proposed system decides which ECC type should be used in TLC and QLC NAND flash in SCM/TLC/QLC NAND flash tri-hybrid SSD, corresponding to various applications and memory capacity ratio. For hm_0 (write- cold application), BCH ECC is enough to correct bit errors in TLC NAND flash. On the other hand, for prxy_0 (write-hot application), LDPC ECC must be applied to TLC NAND flash in case of small SCM capacity, large W/E cycles and high BER in TLC NAND flash. In contrast, this paper concludes that QLC NAND flash needs LDPC ECC regardless of application and memory capacity.