3D QLC NAND Flash

Quad-Level Cell (QLC) NAND stores 4 bits per cell, achieving maximum storage density and the lowest cost per gigabyte of any solid-state NAND technology. The trade-off is reduced write endurance (typically 90–150 TBW per TB) and significantly lower post-SLC-cache sustained write speeds. Used in high-capacity value consumer SSDs: Samsung 870 QVO (SATA), Samsung 990 EVO (NVMe QLC+TLC mix), Crucial P3 (NVMe), WD Blue SN580, and Seagate IronWolf 110. Write performance depends heavily on available SLC write cache; once the cache fills, writes drop substantially.