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Is Octa-Level Cell (OLC) NAND Possible? We May Find Out This Year

posted by martyb on Saturday February 09 2019, @06:51PM   Printer-friendly
from the YMMV dept.

takyon writes:

Wccftech reports that Micron plans to "introduce" NAND with 8 bits (1 byte) per cell:

Back in May of 2018, Micron introduced Quad-Level (QLC) NAND tech and, surprisingly, saw their stock tumble to pricing levels of ~$30 down from ~$60. This was the result of complex NAND pricing and supply/demand factors, not just the introduction of QLC, to be clear. I have just confirmed from multiple sources and stakeholders that Micron is intending to introduce their Octa-Level (OLC) NAND either in Q1 or latest by Q2 2019.

OLC NAND would have 28 (256) states and 28-1 (255) threshold voltages, compared to just 16 states for today's QLC NAND.

3D QLC NAND SSDs arrived on the market in 2018. QLC NAND has lower write endurance, estimated at 1,000 program/erase (PE) cycles, compared to 3,000 P/E cycles for triple-level cell (TLC) NAND, 10,000 P/E cycles for multi-level cell (MLC) NAND, and 100,000 P/E cycles for single-level cell NAND. This exceeds previous expectations of 1,000 P/E cycles for TLC NAND and 100 cycles for QLC NAND. Intel's SSD 660p drives using QLC NAND are rated for only about 0.1 drive writes per day for 5 years, or about 200 TB written on a 1 TB drive. Data retention is also reduced.

In 2013, it was reported that the U.S. Intelligence Advanced Research Projects Activity (IARPA) funded Crocus Technology development of 8-bits-per-cell Magnetic Logic Unit (MLU) memory, which would use two 4-bit layers:

Douglas Lee, VP for system strategy and corporate product development at Crocus, pointed out NAND and MRAM bits-per-cell limitations: "The current semiconductor non-volatile memory state-of-the-art is 3-4 bits per cell, as achieved in NAND flash memory, and is reaching the physical limits of floating gate memory technology. The current state-of-the-art in MRAM is only 1 bit per cell storage."

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  • (Score: 4, Interesting) by takyon on Saturday February 09 2019, @09:01PM (5 children)

    by takyon (881) <takyonNO@SPAMsoylentnews.org> on Saturday February 09 2019, @09:01PM (#798921) Journal

    Sequential read/write speeds would probably drop considerably with OLC NAND, but a fresh and empty drive could operate in SLC, MLC, (TLC?), and QLC modes before finally switching to OLC mode. The IOPS would still be much higher than hard drives.

    Write endurance could be much lower, say 100-500 cycles, but it's not clear that this is too low for a high capacity consumer drive. If you have a 4 TB or 8 TB 3D OLC SSD, you could dump a lot of games and other large applications on there before filling it up. You would probably want to keep archived video on a separate hard drive. On the corporate side, bulky "cold" storage that doesn't get rewritten often can make sense. Facebook in particular wants very dense and cheap ($/TB) NAND storage [tomshardware.com]. For the consumer drives, data retention will probably be a bigger problem than low write endurance. If you leave it alone for a year and a half, will you lose data?

    In the past we've seen reports of "self-healing" NAND [ieee.org] with orders of magnitude more (or indefinite) endurance. If a technology like that makes it out of the lab, it could enable OLC NAND to be used more widely.

    QLC vs. TLC was a 33% increase in storage density. This is 100%, on top of other improvements that will be made, such as 128-256 layers of NAND. So you can start to dream of things like 1 petabyte 2.5" SSDs and 16 terabyte microSD cards.

    This has not been widely reported beyond Wccf, and could be fake, but hopefully we will not have to wait more than a few months to find out if it is real or not.

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  • (Score: 3, Interesting) by krishnoid on Saturday February 09 2019, @09:24PM

    by krishnoid (1156) on Saturday February 09 2019, @09:24PM (#798928)

    For the consumer drives, data retention will probably be a bigger problem than low write endurance. If you leave it alone for a year and a half, will you lose data?

    If these drives had a reliable fail-read-only protocol, even if it was forced near the end of their useful write life, this would be basically a perfect solution. You're unhappy, but at least you can buy a new one, slap the old one into an enclosure, and pull your stuff off. Seems like this would be a good additional option to complement the good backup planning that, er, nobody does at the consumer level [notalwaysright.com].

  • (Score: 0) by Anonymous Coward on Saturday February 09 2019, @11:13PM (3 children)

    by Anonymous Coward on Saturday February 09 2019, @11:13PM (#798945)

    I'm not sure the read/write speeds would drop - TLC is faster than S/MLC. By the time this comes to market it probably will be too. The real concern is endurance like you've said, a few Mb/s read/write either way isn't such a big concern when that's very rarely a bottleneck anymore.