Black SN850 & Blue SN550 in the test: WD's fast SSDs with and without gaming paint

ComputerBase tested two M.2 SSDs with NVMe from Western Digital, which differ significantly in terms of performance and equipment. The WD Black SN850 proves (with reservation) as a high-end alternative to Samsung or the Phison E18 SSDs like the Corsair MP600 Pro and the WD Blue SN550 as an absolute price tip.

Table of contents

1. 1 WDs fast SSDs with and without gaming paint
   1. WD Black SN850: The reigning flagship
   2. WD Blue SN550: NVMe at a low price
   3. HMB against DRAM loss
   4. Key data and prices at a glance
2. 2 Benchmarks, cache analysis and temperatures
   1. Test system and test methodology
   2. Cache analysis (SLC mode)
   3. Copy processes in Explorer
   4. Consistent performance in PCMark 10
   5. CrystalDiskMark
   6. Temperatures over time
3. 3 Conclusion
   1. WD Black SN850, Samsung 980 Pro or Corsair MP600 Pro?
   2. The WD Blue SN550 is a price tip

Update May 21, 2021 12:23 pm

The firmware 613000WD used by ComputerBase in the post-test of the WD Black SN850 with cooler is now available for all SSD owners to download via the WD SSD dashboard. When the update was offered to the sample in the editorial office in April, which had officially been available for a long time for the version without a cooler, it quickly became apparent on the basis of reader feedback in the community that there are obviously two versions of the SN850 without a cooler that differ at least in the identifier – and the second still did not receive the update.

At first there was the suspicion that WD was making a differentiation that was not visible to the customer and that ultimately prevented a firmware update. In consultation with WD, however, this officially turns out to be incorrect. Since Thursday, the firmware is to be offered to all SN850 owners via the dashboard, which the first users in the forum confirm. Why there are two versions of the SN850 without a cooler remains unclear. According to current knowledge, hardware and performance are absolutely identical.

Update 07.04.2021 4:00 p.m.

Firmware 613000WD has also been available for the WD Black SN850 with cooler via the WD Dashboard since Tuesday. As promised by Western Digital, the error when running the Drive Consistency Test in PCMark 10 will be fixed. The test was supplemented by the results and comparative values ​​with the new firmware in all other benchmarks. Significant differences to the old firmware 612000WD are not evident, but when writing full, the new firmware does consistently a few percent better in all three runs (from 0 percent, from 50 percent and from 80 percent fill level).

WD Black SN850: The reigning flagship

The WD Black SN850 is currently the fastest model in Western Digital's SSD portfolio and, like its predecessor, the SN750, serves the enthusiast market, which many manufacturers (sensibly or not) equate with gamers. Via PCIe 4.0 x4, data should be read sequentially at 7,000 MB/s and written at 5,300 MB/s, which applies to the 1 TB model tested here. The 2 TB version writes a little slower at 5,100 MB/s, while the 500 GB version is still 4,100 MB/s.

WD Black SN850 (above), Samsung 980 Pro (below)

SN850: cooling pads on the controller and NAND, but not on the DRAM

With these key data it is clear that the WD Black SN850 has to compete with Phison E18 bolides like the Corsair MP600 Pro (test) or the Samsung 980 Pro (test) with their Elpis controller, which in turn has to be compared to the new PCIe 4.0 Generation count.

The SN850 is equipped with an 8-channel controller, which the manufacturer calls “WD Black G2”. The NAND-Flash is part of the fourth generation of 3D-NAND (BiCS4) from WD and Kioxia and stores 3 bits per cell (TLC) on 96 levels. The DRAM cache has the typical size of 1 GB per 1 TB.

Western Digital offers the SN850 optionally with a cooler, which can delay the point in time until the temperature-related power throttling. This not only means an extra charge of around 20 euros, but also makes the M.2 module a bit wider and, above all, thicker. But there is an optical upgrade, also through the sparingly used RGB lighting on the side.

WD Blue SN550: NVMe at a low price

Aside from the high-end niche for enthusiasts, the WD Blue SN550 is an affordable NVMe model for anyone who wants a faster, but is hardly a more expensive alternative to SATA SSDs. The faster replacement of the older WD SN500 has meanwhile been extended by a model with 2 TB upwards, which the editorial team has tested at this point.

Samsung 980 (above), WD Blue SN550 (below)

According to the manufacturer, the SN550 achieves up to 2,600 MB/s (only 2 TB) for reading and 1,950 MB/s (only 1 TB) for writing via PCIe 3.0 x4. Except for the read rate, the 1 TB model is again the fastest model in the series and also delivers the highest IOPS with random access. In addition to the electrical interface, the lack of a DRAM cache is the biggest difference to the SN850. The differences in performance are mainly due to the WD controller, which is equipped with four instead of eight NAND channels. The storage type is identical to the SN850 with its own 96-layer TLC.

​​HMB against DRAM-Schwund

The “Host Memory Buffer” (HMB) function introduced with the NVMe specification 1.2 is a means of accelerating SSDs without DRAM. The lack of DRAM on the SSD should at least be compensated somewhat by using a small part of the main memory of the host system for the intermediate storage of data from the look-up table (LUT). With the WD Blue SN550, up to 16 MB are reserved as HMB, which from Western Digital's point of view is sufficient for everyday tasks, as the manufacturer has determined in its own analysis (PDF). Samsung uses up to 64 MB as HMB for the SSD 980 (test) without DRAM.

A more recent study (PDF) confirms that HMB for DRAM-less SSDs can increase performance. A direct comparison with DRAM-based SSDs is not possible without the same technical basis, but HMB should not be an equivalent alternative to these. This is why Western Digital still sees SSDs with their own DRAM cache as an advantage for areas of application with higher requirements.

The greatest utilization of host DRAM is to cache mapping information which often only requires tens of MBs of buffer size. While HMB is sufficient for most consumer applications such as working on local files (word documents, excel files) and rendering video files and photos, it may not be viable for all high-end applications or gaming environments. DRAM is still preferable for intensive workloads with random reading and writing of data such as downloading/playing a high-end video game, streaming game play, or executing multiple tasks simultaneously (downloading a program, working on large files and running computer updates).

Western Digital

However, there is no HMB for SATA SSDs. The lack of DRAM there can therefore lead to downright system failures, as ComputerBase noticed years ago with the Toshiba TR200 (test). Other editors also came to the conclusion that SATA SSDs without DRAM are actually not recommended. However, it should look different for NVMe SSDs with HMB support. And in the test of the Samsung 980, the lack of the DRAM cache was probably not noticed negatively thanks to HMB.

Key data and prices at a glance

Despite the large technical and price difference, there is practically the same thing as far as the warranty conditions are concerned. The guarantee period for both series is five years, but expires prematurely if a certain amount of writing (“Total Bytes Written”, TBW) is exceeded. In the case of the WD Black SN850, these TBW are 300, 600 and 1,200 TB for the models with 500 GB, 1 TB and 2 TB of storage space. The WD Blue SN550 has 150, 300, 600 and 900 TB for the models with 250 GB, 500 GB, 1 TB and 2 TB of storage space. In the 500 GB and 1 TB variants, the TBW are identical between the series, the 2 TB version of the SN550 steps out of line with a TBW that is lower in relation to the storage volume.

The WD Blue SN550 is currently one of the cheapest NVMe SSDs with prices of less than 10 cents per GB. The faster WD Black SN850 is around twice as expensive with the same storage capacity.

WD Blue SN550 (above) and WD Black SN850 (below)

WD Black SN850 (above) and WD Blue SN550 (below)

In a direct comparison it becomes clear: The SN550 is not only cheaper, it should also look like this – including a slightly curved PCB. However, this does not affect functionality or compatibility.

Western Digital WD Black SN850 Western Digital WD Blue SN550 Controller: WD Black G2, 8 NAND channels Western Digital, 4 NAND channels DRAM cache: 512 MB available Variant 1,024 MB available Variant 2,048 MB available none Storage capacity: 500/1,000/2,000 GB 250/500/1,000/2,000 GB memory chips: Western Digital? ? TLC (3D, 96 layers) NAND,? Form factor: M.2 (80 mm) Interface: PCIe 4.0 x4 PCIe 3.0 x4 seq. Read: 7,000 MB/s 2,400 MB/s Variant 2,600 MB/s seq. Write: 4,100 MB/s Variant5,300 MB/s Variant5,100 MB/s 950 MB/s variant 1,750 MB/s variant 1,950 MB/s variant 1,800 MB/s 4K random read: 800,000 IOPS variant 1,000,000 IOPS 170,000 IOPS variant 300,000 IOPS variant 410,000 IOPS variant 360,000 IOPS 4K random write: 570,000 IOPS variant 720,000 IOPS variant .000 IOPS 135,000 IOPS variant 240,000 IOPS variant 405,000 IOPS variant 384,000 IOPS Power consumption activity (typ.):? 0.075 W Power consumption activity (max.):? 3.50 W variant 3.90 W Power consumption idle:? 30.0 mW power consumption DevSleep:? no DevSleep power consumption L1.2:? 5.0 mW Functions: NVMe, NCQ, TRIM, SMART, Garbage Collection Encryption: no Total Bytes Written (TBW): 300 terabyte variant600 terabyte variant1,200 terabyte 150 terabyte variant300 terabyte variant600 terabyte variant900 terabyte Guarantee: 5 years Price: from 99 €/from 174 €/from 379 € from 35 €/from 52 €/from 90 €/from 219 € Price per GB: € 0.20/€ 0.17/€ 0.19 € 0.14/€ 0.10/€ 0. 09/€ 0.11

On the next page: benchmarks, cache analysis and temperatures