Western Digital has rapidly risen to being a top-tier player in the market, and this is no more evident than with their newest high-end SSD, the WD Black SN850.

Less than a year after acquiring SanDisk, Western Digital began applying its performance-oriented WD Black branding to SSDs, starting with its first consumer NVMe drive. WD/SanDisk was late entering the consumer NVMe SSD market and its first product was not high-end by the standards of the time. With the second attempt, they got serious and designed their own NVMe SSD controllers, following the same strategy of vertical integration that has worked so well for market leader Samsung. The in-house controller had none of the bugs or performance problems that have plagued the first-generation controllers from most companies. That second-generation WD Black (internally designated SN700) immediately made Western Digital a major player in this market segment, but didn't quite put them at the top: it competed against the Samsung 960 EVO rather than the 960 PRO.

Now after learning some very valuable lessons from the SN700 and its minor refresh SN750, WD is back with the WD Black SN850, the first real hardware upgrade to the Black product line in over two years. Introduced last fall as part of the informal second wave of consumer PCIe 4.0 SSDs, the WD Black SN850 is aimed at the true top of the market, and is designed to compete against the Samsung 980 PRO and a multitude of more recent arrivals mostly based around the Phison E18 SSD controller.

WD Black SN850 Specifications
Capacity 500 GB 1 TB
2 TB
Form Factor M.2 2280 Single-sided
(Optional heatsink)
Interface NVMe PCIe 4.0 x4
Controller WD/SanDisk NVMe G2
NAND Flash Western Digital/SanDisk 96L 3D TLC
Sequential Read 7000 MB/s
Sequential Write 4100 MB/s 5300 MB/s 5100 MB/s
Random Read 800k IOPS 1M IOPS 1M IOPS
Random Write 570k IOPS 720k IOPS 710k IOPS
Warranty 5 years
Write Endurance 300 TB 600 TB 1200 TB
MSRP $119.99 $199.99 $379.99
(with heatsink+RGB) $169.99 $249.99 $469.99

Western Digital doesn't give us detailed performance specifications the way Samsung does, but the basic specifications make it clear that this drive is aimed at the very top: sequential reads up to 7GB/s are pushing the limits of the PCIe 4.0 x4 interface that is still catching on in the consumer market, and random reads at 1M IOPS from a single M.2 drive were just a dream a year ago. Overall, these peak performance specs line up pretty well with the Samsung 980 PRO: Samsung quotes higher random write performance, and WD quotes slightly faster sequential writes.

To reach this level of performance, Western Digital has introduced the second generation of their in-house NVMe SSD controller design. We don't have details of how this controller differs from their first-generation design, but it's a safe bet that almost every part of the chip was substantially upgraded. Compared to the preceding WD Black SN750, the SN850 also benefits from an upgrade to the NAND flash memory, from 64-layer to 96-layer TLC. Western Digital's client OEM SSD product line had already adopted the 96L TLC with the PC SN730, but their retail consumer Gen 3 drives didn't get a matching refresh.

Our review sample is the 1TB WD Black SN850, the capacity with the highest performance specifications. Western Digital sells the SN850 as either a standard M.2 SSD, or as an M.2 SSD with a heatsink and RGB lighting; we're testing the cheaper plain version. The stylized heatsink and RGB lighting adds a lot to the price tag, and we found that both the earlier WD Black SN750 and the competing Samsung 980 PRO perform fine without extra cooling, so we expect the SN850 with the heatsink to be solely a cosmetic upgrade.


The Competition: SSD vs SSD

The most important competitors for the SN850 are other PCIe 4.0 M.2 SSDs. We have results for both the Samsung 980 PRO and the Silicon Power US70 based on the older Phison E16 controller. Our 980 PRO results are using newer firmware than our initial review of that drive, and we've added results for the 2TB model alongside our 1TB results.

Western Digital SN850 1 TB PCIe 4.0 x4 In-House Gen 2
Samsung 980 Pro 1 TB
2 TB
PCIe 4.0 x4 Samsung
Silicon Power US70 1 TB PCIe 4.0 x4 Phison E16

Also of interest are two of the most premium SSDs from the PCIe 3.0 era: the 1.5TB Intel Optane SSD 905P and the Samsung 970 PRO. The 970 PRO was the last high-end consumer drive to use MLC NAND, which gave it a significant advantage on heavy, long-running storage workloads as compared with TLC SSDs that use SLC caching to provide improved peak performance. The 970 PRO is old enough that newer, faster TLC NAND is catching up even in tests where MLC used to be a major advantage—and of course the latest and greatest TLC drives with PCIe 4.0 have far higher peak performance.

Intel Optane SSD 905P 1.5 TB PCIe 3.0 x4 In-House
Samsung 970 PRO 1 TB PCIe 3.0 x4 Phoenix

On the PCIe 4.0 side, the Phison E18 controller is in a number of drives on the market as it was the first PCIe 4.0 NVMe controller to break cover in consumer-focused storage drives with better than PCIe 3.0 speed but not really testing the limits of PCIe 4.0 - plus it is known to be a toasty implementation. Due to a level of system maturity, to date we haven't tested an E18 drive, but our first Phison E18 SSD sample arrived yesterday. We're currently testing through it, especially with the latest firmware which fixes a few issues. That means that this review won't be able to declare an outright winner for the consumer SSD performance crown, but that's not a big deal. Just like when high-end SSDs were all bumping up against the limits of PCIe 3.0, small differences in benchmark scores between today's high-end PCIe 4.0 drives will not be noticeable during any normal real-world usage. These drives are already overkill for most purposes, and which one is technically the fastest is mostly a matter of bragging rights. Also on the market is the novel ADATA XPG Gammix S70 SSD with newcomer Innogrit's high-end SSD controller, which we have in hand but have not yet tested with the latest firmware.

Samsung 970 EVO Plus 1 TB PCIe 3.0 x4 Phoenix
Western Digital SN750 1 TB PCIe 3.0 x4 In-House Gen 1
Western Digital SN730 1 TB PCIe 3.0 x4 In-House Gen 1
Western Digital SN550 1 TB PCIe 3.0 x4 WD Custom (DRAMless)
SK hynix Gold P31 1 TB PCIe 3.0 x4 In House
Kingston KC2500 1 TB PCIe 3.0 x4 SM2262EN
Intel SSD 670p 1 TB PCIe 3.0 x4 SM2265

Representing the more mainstream parts of the consumer SSD market, we have several other Western Digital drives: the WD Black SN750 is the SN850's immediate predecessor, and the SN730 is the OEM counterpart with 96L NAND. The WD Blue SN550 is their second-generation entry-level NVMe SSD, and is one of the best DRAMless SSDs on the market. From other brands: The SK hynix Gold P31 is the current leader for power efficiency and provides performance that saturates its PCIe 3.0 interface. The Kingston KC2500 is one of the faster drives based around the popular Silicon Motion SM2262EN controller, and it uses the same 96L TLC as the SN850. The Intel SSD 670p is more of a low-end drive since it uses QLC NAND, but it's based on a very new generation of 3D NAND and a brand new controller from Silicon Motion which help it achieve great peak performance when using its SLC cache.

Read on over the next few pages for our full review of what ends up being a very speedy drive.

Trace Tests: AnandTech Storage Bench and PCMark 10
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  • Billy Tallis - Friday, March 26, 2021 - link

    A UPS vs power loss protection capacitors defend against slightly different sets of failure conditions, with a lot of overlap. A UPS will help save more data when the utility power goes out, but PLP caps will save data that a UPS couldn't if your PSU blows up or some other component failure inside the PC causes it to crash hard.
  • wr3zzz - Friday, March 19, 2021 - link

    Is there a benchmark that shows "real-world' performance are not worth the premium between PCIe 3.0 and PCIe 4.0? Like how it translates in terms of time saved. CPU benchmark for web page loading is a good example. The benchmark numbers might be 2x or 10x but it doesn't mean anything if it means 1 second vs. 0.1 second. On the other hand, the difference from HDD to SSD is from going minutes to seconds.

    The delta between 4.0 and 3.0 is so wide now. It doesn't do us any good by showing benchmark numbers that are 2x across the board between SN850 and SN750 but then recommend the value proposition just isn't there for PCIe 4.0 in the real world.
  • oRAirwolf - Friday, March 19, 2021 - link

    I do agree that it would be nice if Anandtech would add some real world benchmarks to show use scenarios for the most common tasks like loading Windows, various video game load times, common program launching, etc. I have a very high-end rig but I still boot off of 3 x Samsung 850 evos in RAID 0 because as far as I can tell, there is no significant benefit to switching to an mvne drive for my use case of working from my desktop providing high level tech support and gaming.
  • Oxford Guy - Sunday, March 21, 2021 - link

    You should be able to compare the 'light' workload of 3.0 drives to the 'light' workload of 4.0 drives using their Bench comparison page.

    I'd pay particular attention to latency results. High latency can make things feel slow.

    'The benchmark numbers might be 2x or 10x but it doesn't mean anything if it means 1 second vs. 0.1 second.'

    Not true. .1 second latency (time to wake to do something) is a lot snappier than 1 second latency.
  • Morawka - Friday, March 19, 2021 - link

    Excellent review. See if you guys can a Sabrent Rocket 4 Plus sample and do a review on it! It's supposedly a little faster that the WD 850 in synthetics, but perhaps a little slower in real-world usage. It will be a close match up, that's for sure.
  • Billy Tallis - Friday, March 19, 2021 - link

    I don't have a Rocket 4 Plus, but I have Micro Center's equivalent: Inland Performance Plus. It's currently running The Destroyer, and has already completed the synthetic tests. https://www.anandtech.com/bench/product/2732?vs=27...
  • Oxford Guy - Sunday, March 21, 2021 - link

    Glad to hear there is a firmware update. I wasn't sure that Inland drives would be eligible for them.
  • Spunjji - Friday, March 19, 2021 - link

    "MLC is now dead, and there's no compelling reason to bring it back"

    Oooof, that's gonna chafe the NAND conspiracy-theorists who frequent these hallowed comments 😅
  • Oxford Guy - Sunday, March 21, 2021 - link

    3D fabrication made TLC viable. It has not remedied the deficiencies of QLC and now Intel is reportedly planning to push PLC onto consumers.

    There is nothing theoretical about:

    • The fact that QLC only offers 30% more density, despite having a lot more voltage states than a 30% increase (diminished returns)

    • QLC drives have not been priced low enough to make them worthwhile

    • PLC is going to be worse

    • Economy of scale is actively working against consumer value, by inflating the price of TLC

    Failure of trolling noted.
  • FunBunny2 - Sunday, March 21, 2021 - link

    "There is nothing theoretical about:"

    the fact that, what, no more than a handful make NAND. if they choose, whether through collusion or simultaneous profit-seeking, to sell only QLC and PLC what are you going to do about it? invoke the Defense Production Act to force SLC production at reduced prices? unfettered capitalism never favours the consumer.

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