Vik
February 12, 2018
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Micron Readies 3D QLC NAND-Based Datacenter SSDs for Nearline Storage

Micron has revealed plans to release datacenter-class SSDs based on 3D QLC NAND memory in an effort to compete in the nearline storage market. Briefly announced at a conference last week, the company is taking aim at applications that currently use 7200 RPM HDDs, the use of which is increasingly common in nearline storage. The manufacturer did not reveal any additional details about the upcoming drive, but demonstrated a wafer with QLC 3D NAND dies.

Micron disclosed its plans concerning own-brand SSDs in 2018 at the A3 Technology Live conference in London last week. Among other things, the company intends to introduce a QLC-based SSD with a SATA interface for cloud datacenters this year. The drive will be positioned below the existing 5200-series SSDs and will be aimed primarily at read intensive applications (or the so-called WORM — write once, read many workloads). The QLC-based SSD will have a feature set aimed at hyperscale datacenters and will compete for the place currently occupied by high-capacity 7200 RPM HDDs, reports The Register.

The manufacturer did not disclose capacity of the upcoming QLC-based drives and did not reveal whether they will feature in-house developed controllers with enhanced ECC capabilities (developed using IP and engineers the company got when it acquired Tidal Systems several years ago), or third-party enterprise-grade controllers. The company demonstrated a wafer carrying 64 GB (i.e., 512 Gb) 3D QLC NAND chips, indicating that it has the new flash memory at hand already.

QLC flash memory stores four bits per cell, thus offering a 33% higher bit density and lower per-bit cost compared to TLC flash commonly used for high-capacity SSDs today. 3D QLC NAND has been formally announced by Toshiba and Western Digital so far, but there are no doubts that all producers of NAND are working on QLC chips too. Increasing the bit density of NAND flash usually comes at the cost of endurance, but Toshiba last year said that it had managed to increase endurance of its 3D QLC NAND flash to 1000 program/erase cycles by using a stronger ECC mechanism, which is comparable to endurance of 3D TLC NAND.

QLC’s higher bit densities as well as lower per-bit costs are expected to reduce per-GB prices of high-capacity SSDs further and enable them to compete against existing leading-edge HDDs, such HGST’s Ultrastar with 12 or 14 TB capacity. Two obvious advantages that high-capacity QLC-based SSDs will have when compared to hard drives are lower latencies and higher storage densities. Meanwhile, per-GB costs of HDDs will remain lower when compared to NAND flash for years to come — this is what producers of both HDDs and flash memory agree on. So I’d expect to see that these upcoming 3D QLC NAND-based SSDs will sit between high-capacity HDDs and high-performance SSDs, occupying a tier of their own in hyperscale datacenters.

SK Hynix Announces SSDs with 72-Layer 3D NAND ICs, Own Controllers

SK Hynix this week has said it has completed development of its enterprise-grade SSDs based on its 512 Gb 72-layer 3D TLC NAND chips as well as its own controllers and firmware. The drives will be available with SATA and PCIe interfaces and will target various applications. Select clients of SK Hynix have already received samples of its eSSDs.

SK Hynix’s SATA SSDs are based on the company’s 72-layer 3D NAND 512 Gb chips, and are designed to offer up to 4 TB of raw NAND flash memory. These drives are rated to support sequential read and write speeds of up to 560 MB/s and 515 MB/s respectively. When it comes to random performance, these drives are capable of up to 98K random read IOPS and up to 32K random write IOPS (but SK Hynix does not disclose queue depth and other factors).

As for SK Hynix’s PCIe-based drives, they come in an M.2 form-factor and offer capacities of 1 TB or higher. The manufacturer declares sequential read performance of up to 2.7 GB/s, sequential write performance of up to 1.1 GB/s, random read performance of up to 230K IOPS as well as random write performance of up to 35K IOPS. SK Hynix does not disclose feature set, but based on their images we can expect them to offer power loss protection.

SK Hynix’s Enterprise SSDs at a Glance
	7mm SATA	M.2 NVMe PCIe 3.0
Controller	Proprietary SK Hynix Controllers
NAND Flash	72-Layer 3D TLC NAND
Capacity	Up to 3840 GB	Over 1TB
Sequential Read	560 MB/s	2700 MB/s
Sequential Write	515 MB/s	1100 MB/s
Random Read IOPS	98K	230K
Random Write IOPS	32K	35K
Pseudo-SLC Caching	Supported (?)
DRAM Buffer	Yes, capacity unknown

SK Hynix began production of 72-layer 3D NAND (3D-V4) 512 Gb chips, we believe, in the fourth quarter of 2017, but did not make any formal announcements on the matter. The new chips feature the highest bit density that SK Hynix can offer today and they also offer higher performance compared to predecessors because of a 13.5 MB block size, a reduced tPROG page programming time, and a 667-800 MT/s Toggle 2.0 interface (the manufacturer does not disclose exact data rate of its interface).

SK Hynix does not disclose any details about its datacenter-grade SSD controllers, but it is likely that they were developed by engineers from LAMD, a company that SK Hynix acquired back in 2012. Keeping in mind that we are dealing with 3D TLC NAND-based SSDs, it is highly likely that the controllers support an ECC technology based on an LDPC algorithm.

SK Hynix did not disclose when it expects to ship its enterprise drives to customers, but if its product catalogue is to be believed, the high-capacity SATA drives will be available commercially in the third quarter. Meanwhile, since we are dealing with enterprise SSDs, existing clients of SK Hynix will adopt them when they are satisfied with their real-world performance, reliability, endurance and other factors, so they may start using them ahead of Q3, or later.

Patriot Demos Viper M.2 SSDs with Phison E12, Up to 2 TB

In January, Patriot demonstrated its upcoming Viper M.2-branded high-end SSDs. The new drives are powered by Toshiba’s 64-layer BICS 3D NAND flash memory and Phison’s latest PS5012-E12 controller. The drives will hit the market in the upcoming months and will replace Patriot’s Hellfire SSDs.

Phison yet has to disclose all the details regarding its new PS5012-E12 controller, but at present we do know that the chip is NVMe 1.3 compliant, it supports 8 NAND channels, it has a PCIe 3.0 x4 interface, and is certified to work with the latest types of 3D NAND memory, including Toshiba’s current-gen 64-layer 3D NAND as well as upcoming flash memory from the company. One of the most prominent features of the PS5012-E12 is its support for stronger ECC algorithms based on LDPC method to handle existing and future NAND with even higher bit densities.

The Patriot Viper M.2 uses Toshiba’s 64-layer BICS3 3D TLC/MLC memory and will be available in various configurations ranging from 240 GB all the way to 2 TB. Patriot demonstrated a 512 GB model of the Viper M.2 at CES, which does not fit into a regular lineup that would include 240, 480, 960 GB and 1920 GB models (if this was the case, the “~2 TB”). We contacted Patriot for a clarification after CES, but we have not received any additional information so far. Perhaps Patriot installs 3D NAND ICs of different capacities to build various Viper M.2 drives, but without any additional information it does not make a lot of sense to make guesses.

When it comes to performance, Patriot republishes Phison’s estimates: up to 3200 MB/s sequential read speed, up to 3000 MB/s sequential write transfers as well as up to 600K 4K random read/write IOPS.

Patriot demonstrated its Viper M.2 drives with the retail sticker on, so we expect the SSDs to become available rather sooner than later (Q1-Q2). With an imminent launch, it might suggest that Patriot is up against the clock regarding tuning the Viper M.2’s firmware to differentiate its drives over the other offerings based on the PS5012-E12. This could be a reason why the company publishes performance numbers released by Phison itself. However, the quicker time to market means more intense competition among high-end SSDs from different manufacturers and this will have an effect on prices that is good for consumers.

Plextor Launches M8V SATA SSD

Plextor has introduced the M8V series, their latest budget SATA SSDs, now with 64-layer 3D TLC NAND. Plextor’s budget SATA drives tends to use whatever controller and NAND combination makes the most sense at the time—they aren’t limited to reference designs from the controller vendors, and instead Plextor and parent company Lite-On design their own drives and controller firmware. For this iteration, Plextor has chosen the Silicon Motion SM2258 controller and Toshiba’s 64L 3D TLC NAND flash. Last time around with the M7V it was Toshiba 15nm planar TLC and a Marvell controller, and the preceding M6V used Toshiba 15nm MLC with the Silicon Motion SM2246EN controller. Silicon Motion’s controllers have mostly been used with Intel/Micron 3D NAND recently, so the M8V will provide an interesting opportunity for comparison between two competing 3D NAND designs paired with the same controller.

Plextor M8V Specifications
Capacity	128 GB	256 GB	512 GB
Form Factor	2.5″ SATA and M.2 2280 SATA
Controller	Silicon Motion SM2258
NAND	Toshiba 64-layer 3D TLC
Sequential Read	up to 560 MB/s	up to 560 MB/s	up to 560 MB/s
Sequential Write	up to 400 MB/s	up to 510 MB/s	up to 520 MB/s
4KB Random Read	up to 60k IOPS	up to 81k IOPS	up to 82k IOPS
4KB Random Write	up to 70k IOPS	up to 80k IOPS	up to 81k IOPS
Endurance	70 TBW	140 TBW	280 TBW
Warranty	3 years

In this product segment, Plextor is still sticking with capacities ranging from 128GB to 512GB and three year warranties. Write endurance is rated at a reasonable 0.5 drive writes per day, giving the M8V a total write endurance rating on par with most consumer SSDs that have five year warranties but are rated for only 0.3 DWPD. The M8V is available as a 2.5″ drive with the model number M8VC, or as a M.2 SATA drive with model number M8VG.

Our 512GB sample just arrived and will take its turn on our SSD testbed soon.

Vik
January 30, 2018
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Samsung Launches Z-SSD SZ985: Up To 800GB Of Z-NAND

Samsung announced today that they are officially launching their first Z-SSD product, the SZ985. The Z-SSD uses Samsung’s Z-NAND memory, a high-performance derivative of their 3D NAND flash memory and Samsung’s intended competition for Intel’s 3D XPoint memory. The SZ985 is a high-performance, high-endurance enterprise NVMe SSD.

Samsung has been talking about Z-NAND and the SZ985 for quite a while, including showing off prototypes at several trade shows and conferences. Their initial announcement in 2016 of Z-NAND memory and Z-SSD drives promised 1TB drives in 2016 to be followed by 2TB and 4TB drives in 2017. Today’s launch of 800GB and 240GB models is far behind that initial timeline, but the Z-SSD is finally ready for broad release, almost a year after Intel’s Optane products first hit the shelves. Samsung hasn’t provided much new information about how the Z-SSD works under the hood, but they have disclosed that the drive includes 1.5GB of LPDDR4 DRAM. This suggests that the Z-SSD either has huge overprovisioning with as much as 1.5TB or Z-NAND memory for the 800GB model, or that the Z-NAND is being managed in a way that requires more than the usual 1GB of DRAM per TB of NAND flash used by most SSDs.

Samsung has not provided full performance specifications for the SZ985, but they have highlighted several key metrics that put the Z-SSD in the top performance tier. The SZ985 can deliver up to 750k random read IOPS, well above the 550k IOPS that Intel’s Optane SSD DC P4800X is rated for. Write performance from the SZ985 is much less impressive at only 170k random write IOPS. The random write speed rating on Intel’s P4800X is only 9% slower than the random read speed, while the Samsung SZ985 will have a random write speed that is 77% slower than random reads. Samsung has not been able to overcome all of the limitations of flash memory, but they have produced some impressive improvements.

Samsung also makes a few comparisons against more mainstream enterprise SSDs based on 3D TLC NAND flash memory. The memory cell read performance of their Z-NAND is ten times higher than their 3D TLC NAND, leading to 70% higher random read throughput than their PM963 NVMe SSD. Exact read latency isn’t specified, but write latency on the SZ985 is quoted as 16 µs.

Despite not having record-setting write performance, the SZ985 is still designed to handle very write-intensive workloads. The endurance rating is 30 drive writes per day for five years, matching Intel’s Optane SSD. However, both drives still fall short of the long-gone Micron P320h SLC NAND SSD, in both performance and endurance (though Intel has at least exceeded the random write speed of the P320h). Samsung’s most significant accomplishment with the Z-SSS SZ985 is likely that they can offer the performance of planar SLC at much lower cost thanks to their 3D NAND structure.

Samsung will be presenting the Z-SSD SZ985 at the International Solid-State Circuits Conference, February 11-15.

At Flash Memory Summit last year, Samsung announced a second generation of Z-NAND memory. The SZ985 is still a first-generation product, and drives with the second-generation Z-NAND could still be a long way from launching.

SSDs