Vendor use of Quad Level Cell (QLC) NAND solid-state technology for storage is about economics. With QLC storing more data due to the increase to 4 bits per cell (16 states), the capacity is increased compared to TLC with 3 bits per cell (8 states). This does come at a cost of endurance (effectively the number of writes/erases that can be done) and performance with additional overhead.
Enterprising vendors have addressed the issues brought on with the capacity increase enabled by QLC in interesting ways. Several approaches deliver longevity and performance to enable QLC to be a primary storage technology. The methods implemented have enabled those vendors to give 10-year or similar guarantees on the technology, which has alleviated customer concerns typically brought by competitors without a QLC offering at this point.
Approaches for QLC usage
QLC as a primary storage technology requires a different system design in order to provide the expected performance from current TLC flash and to meet or exceed the lifespan already established. Vendors that offer QLC with the goal to meet the longevity and performance expectations have made the investments in those designs. This does not mean that every vendor QLC storage offering does meet those expectations – some offerings may have much lower numbers and should be considered in a different class of QLC-based storage.
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