Intel and Micron say their quad-level-cell NAND is ready to rip


Intel and Micron jointly announced today that they've begun production and shipments of what they claim is the first quad-level-cell (QLC) NAND flash memory in the industry. With a 64-layer 3D structure, the chips achieve one terabit (125 gigabytes) of density per die. If that's not enough bits for you, the companies also claim that their third-generation 96-layer 3D NAND is in the works to allow for even higher density per die.

Most 3D NAND these days uses triple-level-cell (TLC) NAND and 3D fabrication techniques, so the storage of four bits of information per cell represents a substantial increase in per-cell capacity. The flip side of higher bit capacity per cell is a reduction in write performance due to the increased complexity of programming those cells, as well as a reduction in endurance.


Image: Micron

Intel says that IMFT QLC NAND mitigates these performance liabilities somewhat by using what it calls "CMOS under the array" technology, or CuA. CuA apparently allows Intel and Micron to organize QLC NAND using a greater number of planes—four in IMFT flash versus two in competitors' NAND—and the higher number of planes apparently lets this NAND write more data in parallel.

In any case, Intel isn't making any performance claims for the new media yet, nor is it announcing a shipping product with QLC NAND inside. The company says its product announcements will come later this year at the Flash Memory Summit, to be held August 6 through August 9 in Santa Clara, CA.

Micron, on the other hand, is introducing the 2.5" 5210 Ion SATA enterprise SSD today. The company claims the 5210 is the industry's first shipping drive with QLC NAND inside. The 5210 Ion will have capacities ranging from 1.92 TB to 7.68 TB. Micron says this density will allow businesses to serve read-heavy workloads with higher storage capacities per rack node, all with higher performance and lower latencies than what it calls a comparable setup using multiple 10K-RPM SAS hard drives.


Image: Micron

The company provided sample benchmarks using three read-heavy workloads from the Yahoo! Cloud Serving Benchmark using the Apache Cassandra application. A single Micron 5210 Ion delivers a claimed 2.2x to 3.9x speedup in the number of YCSB operations per second versus that quartet of 10K-RPM drives across those three workloads, all with much lower read latencies than the spinning rust.

The flip side of this arragement is that update operations for QLC NAND are only in the ballpark of the four-hard-drive-per-node legacy configuration that Micron cites. The company cautions that write-heavy workloads will be better served by other products in its lineup. That may be down to not just performance, but also the 1000 program-erase cycles the media can endure. Compare that to 3000 P-E cycles for enterprise TLC NAND and 10,000 P-E cycles for enterprise MLC.

Given these characteristics, it'll be interesting to see whether initial generations of QLC are well-suited to client storage applications given the mix of reads and writes that most users perform on their PCs. Most people aren't performing multiple drive writes per day on their client SSDs, so the extra density afforded by QLC could be just the thing for storing massive data sets like hundreds of Steam games.

Micron says the 5210 Ion is shipping to select customers today, and that broad availability will begin this fall.

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