SK hynix said on 25 August that it has begun mass production of a 321-layer, 2 terabit quad-level-cell (QLC) NAND flash chip, the first QLC device to break the 300-layer threshold. The development phase is complete and global customer validation is under way, with commercial release scheduled for the first half of 2026. By moving from four to six independent planes and stacking 321 layers, the new chip doubles the storage density of current offerings while maintaining performance. SK hynix reports write speeds that are up to 56 percent faster, read speeds 18 percent faster, and overall data-transfer rates twice as high as its previous QLC products. Write-power efficiency is said to improve by more than 23 percent. The company will deploy the device first in PC solid-state drives, then extend it to enterprise SSDs for AI-oriented data centers and to smartphone UFS modules. SK hynix expects the part to strengthen its position in high-capacity, cost-efficient memory as demand for data-hungry AI workloads continues to accelerate.