The Western Digital WD Black SN850 Review: A Very Fast PCIe 4.0 SSD
by Billy Tallis on March 18, 2021 12:50 PM ESTAnandTech Storage Bench - The Destroyer
Our AnandTech Storage Bench tests are traces (recordings) of real-world IO patterns that are replayed onto the drives under test. The Destroyer is the longest and most difficult phase of our consumer SSD test suite. For more details, please see the overview of our 2021 Consumer SSD Benchmark Suite.
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| 99th Percentile Latency | 99th Percentile Read Latency | 99th Percentile Write Latency | |||||||
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The WD Black SN850 starts off with very impressive performance on The Destroyer: only 7.5% slower overall than the Optane 905P and almost twice the overall performance of the Samsung 980 PRO, which is seriously underperforming on this test. The SN850 has great latency scores all around, including for 99th percentile latencies. The SN850 isn't as energy-efficient as Western Digital's PCIe 3.0 SSDs, but is substantially better than the 980 PRO or the Phison E16-based Silicon Power US70.
AnandTech Storage Bench - Heavy
The ATSB Heavy test is much shorter overall than The Destroyer, but is still fairly write-intensive. We run this test twice: first on a mostly-empty drive, and again on a completely full drive to show the worst-case performance.
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| 99th Percentile Latency | 99th Percentile Read Latency | 99th Percentile Write Latency | |||||||
| Energy Usage | |||||||||
On the Heavy test, the WD Black SN850 again comes in second place for overall performance, behind the Optane 905P. Its lead over the other PCIe 4.0 drives is smaller and the 980 PRO surpasses it in some of the latency metrics, but overall the differences between the SN850 and the 980 PRO would seldom be noticeable to the end-user during this kind of heavy workload. The SN850 again has a clear energy efficiency lead over the other PCIe 4.0 drives.
AnandTech Storage Bench - Light
The ATSB Light test represents ordinary everyday usage that doesn't put much strain on a SSD. Low queue depths, short bursts of IO and a short overall test duration mean this should be easy for any SSD. But running it a second time on a full drive shows how even storage-light workloads can be affected by SSD performance degradation.
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| Average Latency | Average Read Latency | Average Write Latency | |||||||
| 99th Percentile Latency | 99th Percentile Read Latency | 99th Percentile Write Latency | |||||||
| Energy Usage | |||||||||
The WD Black SN850 is tied for first place when the Light test is run on an empty drive, but its full-drive performance is better than any of the other drives except the Optane SSD. The latency scores are all top-notch, though the 99th percentile read latency is a bit higher than the other PCIe 4.0 SSDs. As with the other ATSB tests, the SN850 uses less energy than the other PCIe 4.0 drives, but isn't as efficient as some of the good PCIe 3.0 SSDs.
PCMark 10 Storage Benchmarks
The PCMark 10 Storage benchmarks are IO trace based tests similar to our own ATSB tests. For more details, please see the overview of our 2021 Consumer SSD Benchmark Suite.
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| Full System Drive | Overall Score | Average Bandwidth | Average Latency | ||||||
| Quick System Drive | Overall Score | Average Bandwidth | Average Latency | ||||||
| Data Drive | Overall Score | Average Bandwidth | Average Latency | ||||||
The WD Black SN850 has a clear lead over other flash-based SSDs in all three PCMark 10 Storage tests. It has a larger SLC cache than most 1TB drives, and it's just large enough to contain all the writes from these tests. The SN850 beats even the higher-capacity drives because its cache is faster than most in addition to being large. The SN850 comes closest to matching the Optane SSD's performance on the Data Drive test that focuses relatively more on sequential IO, where the SN850 offers twice the throughput of the Optane 905P.
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lmcd - Thursday, March 18, 2021 - link
*a faster, but not substantially faster, SSD that consumes nearly 2x the power.ozzuneoj86 - Friday, March 19, 2021 - link
Absolutely agree for laptops.For desktops, I think I'd need to see a review that measured thermals, overall system temperature and cooling noise as well as performance. Sure more performance is technically better, but if it is only noticeable in synthetic benchmarks (for now), adding several more watts of heat output to the area between your CPU and GPU isn't the best thing. Also, not having to worry as much about your SSD if ambient temps get a bit toasty is nice too.
For the record, if prices were close I would still opt for more speed unless it was a really huge thermal\power penalty. At this point though, the $65-$90 (depending on sales) price difference is quite large. There's some wisdom in waiting for applications to start utilizing ultra high speed NVMe storage before investing extra money in it.
Kind of like buying 64GB of RAM for future proofing. By the time you need it, RAM is faster and cheaper per GB.
artifex - Thursday, March 18, 2021 - link
I'm hoping they'll make denser 3.0x4 offerings for the laptop space, especially if they can keep a lower power profile and decent thermals. I won't care about 4x4 until I'm upgrading to AM5 on my desktop, probably.Kamen Rider Blade - Thursday, March 18, 2021 - link
All this review does is make me want Optane even more.That sheer utter consistency is what I'm looking for.
And that sweet low latency.
Tomatotech - Thursday, March 18, 2021 - link
Sadly Optane is dying. Micron has just abandoned 3D Xpoint, and Intel completely messed up their dual drives and most of the Optane range is MIA.This WD 850 gives you almost as much performance as Optane in the office or at home, at at a fraction of the price. There are other server orientated SSDs that are also becoming almost as good as Optane in the server space, again at far cheaper prices. It’s sad, I had high hopes for Optane but it seems Intel couldn’t scale it out.
ksec - Friday, March 19, 2021 - link
And this Optane 905 isn't even that "great" so to speak. ( Even though it is very expensive, think of it as low cost Optane ) I want to see how Optane PX5800 perform.With that said, I am very suspired at the latency WD has managed to achieve. Even for Professional and enthusiast, it will be more than enough for 90+% of use case.
Spunjji - Friday, March 19, 2021 - link
For what purpose?arashi - Sunday, March 21, 2021 - link
Epeen.FatFlatulentGit - Thursday, March 18, 2021 - link
No Sabrent Rocket 4 Plus in the benches? I'm baffled that it's not there seeing as how it's probably the most likely competitor for this drive.Billy Tallis - Thursday, March 18, 2021 - link
As I mentioned in the article, my first Phison E18 drive arrived yesterday and I don't have complete results yet. But the first batch of results is in Bench: https://www.anandtech.com/bench/product/2732?vs=27...