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
(Reviewed)
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
Elpis
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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  • Oxford Guy - Monday, March 22, 2021 - link

    What am I going to do about it? Tell the truth, aka whinge. Reply
  • Beaver M. - Friday, March 19, 2021 - link

    I heard reports that WD SSDs cant do Windows sleep, which is a reason why Samsung did their own NVMe driver. Can you confirm that? Reply
  • Endgame124 - Friday, March 19, 2021 - link

    What this review really says is we need less TLC drives, and either flat out all SLC drives or a new revision of the Optaine 905P. Reply
  • Oxford Guy - Sunday, March 21, 2021 - link

    SLC shouldn't be so drastically faster than TLC if MLC is not.

    So, if the data does indeed suggest what you're saying then it suggests that Samsung's implementation of MLC is lacking. MLC should be between SLC and TLC in performance, not 'dead' (equivalent to TLC).
    Reply
  • MS - Sunday, March 21, 2021 - link

    I appreciate the idle power numbers but they are really meaningless. Why don't you show sequential and random write power consumption which should be in the 25 to 40 W range. Until the drive starts heating up and the performance collapses as a consequence of thermal throttling. Anything else is, er, marketing collateral at best Reply
  • Billy Tallis - Sunday, March 21, 2021 - link

    What are you talking about? The power numbers reported here are for the drive itself, not the whole computer system's wall power consumption. Even the Optane SSD included in this review doesn't hit 25W, let alone 40W. M.2 drives rarely break 8W. SATA SSD usually stay under 5W. And the idle power numbers are not at all meaningless; consumer SSDs spend the overwhelming majority of their time idle. Reply
  • kumataro - Thursday, March 25, 2021 - link

    So the SN850 is faster when it is brand new and has > 80% free space... once the drive starts to get full the Samsung 980 Pro has better performance? Reply
  • 529th - Sunday, April 11, 2021 - link

    Just picked up a SN850, and the model number is WDBAPY0010BNC, however it was advertised as the model in this review, the WDS100T1X0E. What did I just buy?

    I've seen articles about companies changing part revisions that are not as fast as the ones sent out for reviews.
    Reply
  • mrplus - Wednesday, April 14, 2021 - link

    Hi, guys, lame question – does this pci-4 thing means that I need a new pci-4-friendly controller to use it? Or it’s just completely internal matter and any - for example - pci-friendly-usb3.2 external case will work with it? Reply
  • Billy Tallis - Thursday, April 29, 2021 - link

    PCIe is backwards-compatible: the host and the device will negotiate the highest link speed and widest lane count that are supported by both end points. So a Gen4 SSD in a motherboard that only supports Gen3 will work fine, limited to Gen3 speeds. A Gen4 SSD in a USB to NVMe enclosure that only provides PCIe Gen3 x2 to the drive will likewise be compatible, but with severely crippled performance. Reply

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