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.
 |
|||||||||
| Average Data Rate | |||||||||
| 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 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.
 |
|||||||||
| Average Data Rate | |||||||||
| 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.
 |
|||||||||
| Average Data Rate | |||||||||
| 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.
 |
|||||||||
| 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.
Facebook
Twitter
RSS
83 Comments
View All Comments
Samus - Tuesday, March 23, 2021 - link
eva: true. SATA hasn't been updated in over a decade (unlike SAS) and it'll be some time before consumer-class drives can saturate a 6Gbps link (currently almost none can even saturate a 3Gbps link.)With MAMR, HAMR, etc coming to market, performance is finally going to increase where areal density was historically the only way sequential transfers went up, so drives might start cracking SATA2 bandwidth. I suspect when drives near SATA3 bandwidth, it'll either be so long from now that hard disk technology in the consumer space will be dead (replaced by cheap NAND storage) as hard disk technology seems to be focusing on data centers where SAS is common and already capable of 12Gbps+, or consumers that wish to actually use magnetic disk storage will adopt SAS.
Molor1880 - Thursday, March 18, 2021 - link
2.5 in drives and U.X won't make a comeback outside a server room, which is what that combination is designed for. The trend for personal devices is smaller and lighter, not bigger and bulkier. I would expect M.2 and gum stick drives to evolve, in step with PCIe, but it's not going away for at least another decade.Tomatotech - Thursday, March 18, 2021 - link
2.5” is dead for casual home use. I used to think it had a place in the office, but with the rise of laptop-powered WFH and the popularity of space-saving small SFF computers for the office I don’t see it as having a future.Your point about cost makes no sense. 2 TB+ of SSD chips is expensive. It makes no difference whether it’s on an m.2 stick or in a half empty U.3 case, it costs the same either way. With U.3 there’s a (small) extra cost for the packaging, plus the extra wires and extra ports required and extra assembly steps. Might be worth it in the datacentre but not for price-sensitive home or office market where 99% of drives are never swapped.
Tomatotech - Thursday, March 18, 2021 - link
Ninja’d by Molor1880!WaltC - Thursday, March 18, 2021 - link
I think M.2 is here to stay. You are looking for economies of scale in NVMe M.2 drive capacity--that will happen as time goes on. It's remarkable to me how fast M.2 drives have ratcheted up in performance and capacity already. But, hey, if you need the economic capacity there's always the old 7200 rpm standby, right? These super-capacity drives will be around for a long while--but eventually M.2 will supplant them, imo.My older PCIe3 960 EVO M.2 boot drive would throttle regularly in large tasks, like doing a full AV Defender scan on C:\. The drive always crashed and never completed a full C:\ scan. This doesn't happen with the 980 Pro at all, and it's running in the same mboard and in the same slot the 960 ran in--using the same heatsink--just a flat sink that came with the mboard. Things are improving rapidly on the NVMe M.2 front, imo.
damianrobertjones - Friday, March 19, 2021 - link
"Threw is the past tense of the verb throw. It’s the word you use to say that something threw you for a loop or threw you off. Through is an adverb and a preposition. It’s used to say that you entered on one side of something and exited on the other."Not sure if 2.5" drives have gone anywhere?
twotwotwo - Wednesday, April 21, 2021 - link
There are a few 4 and 8TB m.2 drives out already, so a stick with more than 2TB might be practical for you before any switch to the mostly-enterprise u.3 form factor. Not that there's anything wrong with holding on to your current stuff! :)Makaveli - Thursday, March 18, 2021 - link
"Later this year we're expecting another wave of Phison E18 drives to arrive using 176L 3D TLC NAND"This is what i'm waiting to see.
I don't like that all the new generation drives also all took a reduction in TBW and all seem to have smaller SLC caches minus this WD drive.
ozzuneoj86 - Thursday, March 18, 2021 - link
With the SK Hynix P31 performing so well for the money, especially in efficiency, I'll be keeping an eye out for PCI-E 4.0 offerings from them.I'm currently booting from a 2.5" MX500 1TB. Since I have an X570 board, it feels like my next drive purchase should be PCI-E 4.0. Thankfully, I doubt these things provide any appreciable difference in performance over a good SATA SSD for the vast majority of applications I use, so I can stand to wait for the prices to come down. Given the choice between buying a 1TB SSD with blistering fast performance for $200, or one that generally benchmarks lower but uses less power, runs cooler and provides an almost identical experience for $135 (with sales often much lower)... its hard to justify the more expensive one.
lmcd - Thursday, March 18, 2021 - link
Imo in a laptop it's impossible to justify a faster SSD that consumes more power.In a desktop, though, I can see it making sense for certain workloads.