SK hynix Launches PQC21 cSSD Featuring 321-Layer QLC NAND Technology

SK hynix has begun shipping its PQC21 cSSD, marking a significant milestone as the first commercial product built on the company’s advanced 321-layer QLC (Quad-Level Cell) NAND flash technology. Available in 1 TB and 2 TB capacities, the PQC21 cSSD is initially being supplied to Dell, with shipments starting this month. This launch positions SK hynix at the forefront of next-generation solid-state drive (SSD) innovation, targeting both enterprise and consumer storage markets.

Advancements in QLC NAND Flash

QLC NAND technology stores four bits of data per cell, significantly increasing storage density compared to TLC (Triple-Level Cell) NAND, which stores three bits per cell. While QLC offers higher capacity and cost efficiency, it has traditionally faced challenges with write performance and endurance. SK hynix addresses these concerns by implementing SLC (Single-Level Cell) caching within the PQC21 cSSD. This approach allows frequently accessed data to be written first to faster SLC-mode regions before being moved to the QLC cells, effectively narrowing the performance gap and delivering smoother operation for typical workloads.

According to research from International Data Corporation (IDC), QLC NAND is poised for rapid adoption in the coming years. IDC projects that QLC NAND will account for 22% of the global client SSD (cSSD) market in 2025, rising sharply to 61% by 2027. The introduction of the PQC21 cSSD aligns with this trend, as SK hynix prepares to expand its customer base beyond Dell as production ramps up.

In the broader NAND flash market, Samsung remains the leading supplier, generating $6.6 billion in revenue last quarter—a 10% increase quarter-over-quarter. However, Samsung’s market share slipped to 28% due to a temporary decline in bit shipments during a process transition. Meanwhile, SK Group, which includes SK hynix and Solidigm, recorded the strongest growth among the top five NAND vendors. The group’s revenue surged by 47.8% quarter-over-quarter to approximately $5.21 billion, with market share climbing to 22.1%. This growth was driven by robust demand for mobile NAND and enterprise SSD solutions.

Looking Ahead

The launch of the PQC21 cSSD underscores SK hynix’s commitment to advancing NAND flash technology and meeting the evolving needs of data-intensive applications. As QLC NAND adoption accelerates, innovations like SLC caching will play a crucial role in balancing performance, capacity, and cost, shaping the future of SSD storage for both enterprise and consumer markets.