Unfortunately — and this is simply a function of how NAND works — there’s no way to boost storage capacity by increasing the amount of data stored per cell without simultaneously whacking performance. As the number of bits of information in the cell rises, the number of discrete voltage levels programmed within that cell rises as well. The more voltage levels, the longer it takes to program the NAND and the more careful the controller has to be about not inappropriately overwriting adjacent cells when performing writes. Anandtech has a review of the new drives and their specifications and pricing:
Just as with TLC, SLC (single-level cell) caching is being used to improve drive performance. By having a small partition of SLC NAND on-drive, Intel can accelerate most common use cases while still offering low-cost storage capability. This actually required AT to change its test protocol — at low storage fill rates, the drive mostly treats the QLC drive as an SLC cache. As the drive fills, the amount of space available for SLC caching drops and the drive’s performance drops with it.
The graph here is from just one benchmark (we highly recommend reading the whole review), but it shows the split between when the SLC cache is available and when it isn’t. If you keep this drive lightly loaded, it offers amazing performance, often competing well against other, much more expensive NVMe drives. If you load it to nearly full, performance can drop precipitously. However, as AT notes, it’s actually rare for drives to be hammered this much. Most users have relatively light storage workloads, and a flexible drive like this can offer high performance through most of its capacity.
The one reason to hold off would be to see if QLC drives have any of the problems that plagued TLC drives early in their lives. I don’t want to overdraw the comparison here, because there’s been one major change: When TLC drives like the 840 Evo ran into problems, they were being built on 20nm planar NAND. Today, we’re using 3D NAND on a larger process to manufacture the drives. That’s what made QLC possible in the first place, and it’s why it may not be accurate to assume problems with TLC will lead to issues with QLC. All the same, caveat emptor — at least for now. Be advised that in the past, changing voltage values over time have required drives to receive firmware updates to preserve performance.