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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| Average Latency | Average Read Latency | Average Write Latency | |||||||
| 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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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.