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Intel Launches First Consumer QLC NAND SSD

Intel's first quad-level cell (QLC) SSD for consumers is now available. Is it time to jump for the latest in storage technology?
By Joel Hruska
Intel-QLC-Feature

There are two ways to improve SSD storage density now that pretty much every firm is on board with 3D NAND: Stack more layers of NAND on top of each other, or store more data per NAND memory cell. Advances in the latter have been few and far between. Originally, SSDsSEEAMAZON_ET_135 See Amazon ET commerce(Opens in a new window) stored just one bit of data per cell. MLC NAND had to be developed (two bits of storage) before the drives began to proliferate, and TLC (triple-level cell) took NAND mainstream. Now Intel is the first company to launch a consumer QLC (quad-level cell) drive, and while Micron led with an enterprise offering earlier this year, a new QLC product is still a major first. The new Intel 660p is a replacement for the earlier 600p series.

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(Opens in a new window) of the new drives and their specifications and pricing:

660p-specs Image by Anandtech(Opens in a new window)

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.

heavy-latencyIn most cases, the penalty for a full drive is not this bad, but the spread between empty and full performance is often large.

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.

Now Read:  Micron's 5210 Enterprise SSD Packs Industry's First QLC NAND, Intel Leak Confirms Upcoming SSDs Will Use Ultra-Dense QLC NAND, and How Do SSDs Work?

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