Home / Tech News / Featured Tech News / WD Blue SN550 1TB SSD Review

WD Blue SN550 1TB SSD Review

Rating: 8.0.

WD launched the first NVMe drive for the mainstream Blue range in April 2019, the SN500. Today we have the next generation Blue NVMe drive, the SN550 in for review. Just like its SN500 predecessor, it uses a combination of WD’s own in-house controller and 3D TLC NAND.

Watch via our Vimeo channel (below) or over on YouTube at 2160p HERE

The new SN550 not only sees an increase in capacity from the SN500, but more importantly, the new drive has a PCIe x4 interface rather than a x2 interface and it ditches the 64-layer 3D TLC NAND in favour of 96-Layer 3D TLC NAND. At launch, there are three capacities in the SN550 range – a 250GB, 500GB and the flagship 1TB drive we are looking at here.

WD quote Sequential read/write performance (QD32 T1) for the range as up to 2,400MB/s for all three drives with writes varying with capacity; 250GB, 950MB/s, 500MB, 1,750MB/s with the 1TB drive rated at up to 1,950MB/s.

Random read performance (QD32 T8) for the SN550 range is quoted as up to 170,000 IOPS for the 250GB drive, 300,000 IOPS for the 500GB drive and up to 410,000 IOPS for the 1TB drive. Random write figures for the range are; up to 135,000 IOPS for the 250GB drive, 240,000 IOPS for the 500GB drive and up to 405,000 IOPS for the 1TB drive.

Endurance for the 1TB drive is quoted at 600TBW and WD backs the drive with a 5-year warranty.

Physical Specifications:
Usable Capacities: 1TB.
NAND Components:  SanDisk 96-layer 3D TLC.
NAND Controller: WD NVMe.
Cache: none.
Interface: PCIe Gen 3 x4
Form Factor: 2280  M.2.
Dimensions: 22 x 80 x 2.3mm.
Drive Weight: 6.5g.

Firmware Version: 211000WD.


The WD Blue SN550 comes in a smallish box with a clear image of the drive on the front. In the bottom left corner of the box, the 2,400MB/s Sequential read figure is highlighted. Next to this are three boxes displaying the capacity of the drive (in this case 1TB), the fact it uses 3D NAND and that it comes with a 5-year warranty.

The rear of the box has a small clear plastic panel through which part of the drive is visible, sitting in its protective plastic enclosure. The only other thing in the box is a Technical Support and Warranty Guide.


WD’s Blue SN550 is a single-sided PCB design, so the rear of the drive is empty and to be honest so is much of the front. Being a DRAM-less design, the only two major chips on the board are the in-house WD controller (SanDisk 20-82-01008-A1) which sits on the PCB just behind the interface contacts and a single 1TB NAND package of SanDisk 96-layer 3D TLC NAND which is housed at the other end of the PCB.

WD’s SSD management utility goes under the name of SSD Dashboard. With it, you can monitor drive status, performance, update firmware and monitor temperatures. There’s no cloning tool integrated into the utility but you can download Acronis True Image WD Edition from the WD website.

For testing, the drives are all wiped and reset to factory settings by HDDerase V4. We try to use free or easily available programs and some real world testing so you can compare our findings against your own system.
This is a good way to measure potential upgrade benefits.

Main system:
Intel Core i7-7700K with 16GB of DDR4-3200 RAM,
Sapphire R9 390 Nitro and an Asus Prime Z270-A motherboard.

Other drives
Corsair Force MP500 480GB
Corsair Force MP510 960GB
Crucial P1 1TB
Gigabyte Aorus RGB 512GB
Intel Optane SSD900P 480GB
Intel Optane SSD905P 480GB
Intel SSD760p 512GB
Kingston A1000 480GB
Lexar NM600 480GB
Plextor M9Pe(Y) 512GB
Plextor M8PeG 512GB
Patriot Viper VPN4100 1TB (PCIe Gen4)
Patriot Viper VPN100 1TB
PNY CS3030 1TB
PNY CS2030 240GB
Seagate FireCuda 510 1TB
Samsung SSD970 EVO 2TB
Samsung SSD970 PRO 1TB
Samsung SSD960 PRO 2TB
Samsung SSD960 EVO 1TB
Samsung SSD960 EVO Plus 1TB
Toshiba BG4 1TB
Toshiba XG6 1TB
Toshiba OCZ RD400 512GB
Western Digital Black SN750 1TB
Western Digital Black SN750 1TB with Heatsink
Western Digital Black NVMe 1TB
Western Digital Blue SN500 500GB

Atto Disk Benchmark 3.05. / 4.0
CrystalMark 6.0.0.
AS SSD 2.0.
Futuremark PC Mark 8

All our results were achieved by running each test five times with every configuration this ensures that any glitches are removed from the results. Trim is confirmed as running by typing fsutil behaviour query disabledeletenotify into the command line. A response of disabledeletenotify =0 confirms TRIM is active.

CrystalDiskMark is a useful benchmark to measure theoretical performance levels of hard drives and SSD’s. We are using v6.0.

The new SN550 drive is not only faster than the previous generation Blue SN500, but it’s also faster than both versions of the WD Black SN750 drive at a fairly deep queue depth of 32 in CrystalDiskMark.

At a QD of 1, the SN550 has a slightly faster read performance than the SN500 and both WD Black SN750’s but the SN750 has slightly better write performance.

We are also starting to test with the latest version 7 of CrystalDiskMark which has a couple of built-in profiles, Peak Performance and Real World.



The test results from CrystalDiskMark 7 confirm the official figures for both Sequential (up to 2,400MB/s reads, 1,950MB/s writes) and 4K random (up to 410,000 IOPS reads, 405,000 IOPS writes) performance.

The real-world profile Sequential results are a little lower than both the default and peak performance results but that is due to the test being done at a QD of 1 with 1 thread, which is where most of the everyday tasks are undertaken.

The ATTO Disk Benchmark performance measurement tool is compatible with Microsoft Windows. Measure your storage systems performance with various transfer sizes and test lengths for reads and writes. Several options are available to customize your performance measurement including queue depth, overlapped I/O and even a comparison mode with the option to run continuously.

Use ATTO Disk Benchmark to test any manufacturers RAID controllers, storage controllers, host adapters, hard drives and SSD drives and notice that ATTO products will consistently provide the highest level of performance to your storage.

We are using version 3.5 for our NVMe disk tests but we are in the process of upgrading to the 4.0 version so we’ve included a chart with the drives we have so far tested with the 4.0 version.

The official Sequential read/write figures for the drive are up to 2,400MB/s for reads and up to 1,950MB/s for writes, both figures we can confirm using the ATTO benchmark with the review drive producing read/write figures of 2,452MB/s and 2,064MB/s respectively when tested.

The drive scores slightly lower in the 4.0 version of ATTO with reads at 2,280MB/s and writes at 1,920MB/s.

AS SSD is a great free tool designed just for benching Solid State Drives. It performs an array of sequential read and write tests, as well as random read and write tests with sequential access times over a portion of the drive. AS SSD includes a sub suite of benchmarks with various file pattern algorithms but this is difficult in trying to judge accurate performance figures.

With its read/write scores of 1446 and 1898 respectively, the new SN550 is comfortably faster than previous SN500 drive.

IOMeter is another open-source synthetic benchmarking tool which is able to simulate the various loads placed on the hard drive and solid-state drive technology. There are many ways to measure the IOPS performance of a Solid State Drive, so our results will sometimes differ from the manufacturer’s quoted ratings. We do test all drives in exactly the same way, so the results are directly comparable.

We test 128KB Sequential read and write and random read and write 4k tests. The test setup’s for the tests are listed below. Each is run five times.

128KB Sequential Read / Write.
Transfer Request Size: 128KB Span: 8GB Thread(s): 1, Outstanding I/O: 1-32 Test Run: 20 minutes per test

4K Sustained Random Read / Write.
Transfer Request Size: 4KB Span: 80GB Thread(s): 4, Outstanding I/O: 1-32 Test Run: 20 minutes per test

4K Random 70/30 mix Read/Write.
Transfer Request Size: 4KB Span: 80GB Reads: 70% Writes: 30% Thread(s): 4 Outstanding I/O: 2 – 32 Test Run: 20 minutes.

128KB Sequential Read / Write Performance

In our own Sequential tests, the read performance peaks at 2,417.61MB/s, very slightly above the official figure of 2,400MB/s. Writes peak at 2079.49MB/s, again higher than the official 1,950MB/s.

128KB Sequential Read Performance Compared

At Queue Depth’s 1 and 2, the WD Blue SN550 is not only much faster than the previous SN500 drive, it is also faster than both versions of the WD Black SN750 we’ve tested. However, at a QD of 32, the SN550 as you might expect drops back compared to the two Black SN750 drives.

128KB Sequential Write Performance Compared

At a QD of 1, the SN550 shows very strong performance not only compared to the previous SN500 but to both SN750 Black drives, However as the QD deepens the two Black model drives pull away from the SN550 but it still remains much faster than the older SN500 thanks to its PCIe x4 interface and 96-layer NAND.

4K Random Read v QD Performance

The official 4K random read rating for the 1TB SN550 is up to 410,000 IOPS. This maximum figure was obtained by testing the drive at a QD of 32 using 8 threads. However, our standard 4K random testing is done with 4 threads, so we couldn’t match that maximum IOPS figure, The best figure we got was 244,020 IOPS at a QD of 32. We did, however, run some quick tests at QD32 8T getting a figure of 424,903.3 IOPS, even faster than the official maximum.

4K Random Read v QD Performance Compared.

Thanks to the PCIe x4 interface that the SN550 uses instead of the x2 interface employed by the SN500, the SN550 is much faster throughout the tested queue depths.

4K Random Write v QD Performance

As with the random read test, we couldn’t get close to the official 405,000 IOPS maximum random write figure, the best we saw with our standard testing was 204,873 IOPS. However, once again testing the drive with the same QD and number of threads that was used to get the official ratings, the review drive produced a figure of 403,767.8 IOPS.

4K Random Write v QD Performance Compared.

At a QD of 1, the SN550 Blue is faster than both versions of WD’s SN750 Black drive as well as the older SN500 Blue drive. However, as the queue depth deepens the SN550 is left behind the two Black drives.

4K 70/30 Mixed Performance

The WD Blue SN550 performs well in the 4K 70/30 mixed read/write test, peaking at 108,470 IOPS (444.29MB/s).

In our read throughput test the WD Blue SN550 peaks at 2,156.62MB/s at the 4MB block size before dropping back. That peak figure is a little shy of the maximum official figure of 2,400MB/s.

Peak write throughput comes at the 256KB block size at 2,064.35MB/s, which is a bit better than the official maximum of 1,950MB/s

Just to see a bit more clearly how the new drive compares to the previous generation Blue drive and the two versions of the SN750 Black drive, we’ve pulled out their results into charts of their own.

The new Blue SN550 drive’s read performance sits neatly between the previous generation Blue SN500 and the two performance Black SN750 drives. The SN550 suffers a small dip in performance at the 512KB block mark but soon recovers.

The Blue SN550 performs well in the write throughput test until the 256KB block mark where the performance begins to tail off. As with the read test, the new drive is much faster than the previous SN500 Blue drive.

Futuremark’s PCMark 8 is a very good all-round system benchmark but it’s Storage Consistency Test takes it to a whole new level when testing SSD drives. It runs through four phases; Preconditioning, Degradation, Steady State, Recovery and finally Clean Up. During the Degradation, Steady State and Recovery phases it runs performance tests using the 10 software programs that form the backbone of PCMark 8; Adobe After Effects, Illustrator, InDesign, Photoshop Heavy and Photoshop Light, Microsoft Excel, PowerPoint, Word, Battlefield 3 and World of Warcraft. With some 18 phases of testing, this test can take many hours to run.

The drive is written sequentially through up to the reported capacity with random data, write size of 256 × 512 = 131,072 bytes. This is done twice.
Run writes of random size between 8 × 512 and 2048 × 512 bytes on random offsets for 10 minutes. It then runs a performance test. These two actions are then repeated 8 times and on each pass the duration of random writes is increased by 5 minutes.
Steady State
Run writes of random size between 8 × 512 and 2048 × 512 bytes on random offsets for final duration achieved in degradation phase. A performance test is then run. These actions are then re-run five times.
The drive is idled for 5 minutes. Then a performance test is run. These actions are then repeated five times.
Clean Up
The drive is written through sequentially up to the reported capacity with zero data, write size of 256 × 512 = 131,072 bytes.

Overall the drive doesn’t handle the rigours of PCMark 8’s Consistency Test too well during the Degradation and Steady State phases. The Recovery phase is handled much more impressively although the performance is erratic.

PCMark 8’s Consistency test provides a huge amount of performance data, so here we’ve looked a little closer at how the WD SN550 performs in each of the benchmarks test suites.

Adobe Creative Cloud

The drive gets hit hard during the Adobe CC test phases and although the bandwidth trace for the two PhotoShop traces is quite smooth, the actual bandwidth is pretty low and the Recovery phase is very erratic. The other apps suffer throughout the Degradation and Steady-State phases. The best recovery phase in terms of stability is for the Indesign trace.

Microsoft Office

Usually, in the MS Office test, it’s the Word trace that causes a drive problems. Although in the case of the SN550 the bandwidth is pretty low during the test run, it’s fairly consistent which is something you can’t say about the Excel and PowerPoint traces which seem to cause the drive real problems.

Casual Gaming

The SN550 handles the World Of Warcraft trace much more efficiently than the Battlefield 3 one, whose performance is very erratic.

Just like the Consistency test, PCMark 8’s Standard Storage test also saves a large amount of performance data. The default test runs through the test suite of 10 applications three times. Here we show the total bandwidth performance for each of the individual test suites for the third and final benchmark run.

The drive produces some strong bandwidth figures for PCMark 8’s Standard Storage test, especially for the two Adobe Photoshop tests.

When it comes to the total bandwidth performance figure, the SN550 is some 121.51MB/s faster than the previous SN500 drive.

For the long term performance stability test, we set the drive up to run a 20-minute 4K random test with a 30% write, 70% read split, at a Queue Depth of 256 over the entire disk. The 1TB WD Blue SN550 averaged 43,290 IOPS for the test with a very respectable performance stability of 82.8%.

The 1TB WD Blue SN550 cache fills with data at around 13GB of writes, with the performance dropping to an average of 871MB/s after the cache is full.

To see what performance effects if any, happen as the drive’s capacity gets used up, we tested the drive at 25%, 50%, 75% and 90% capacity.

Using the ATTO benchmark to test the Sequential performance as the drive fills shows that there is no real deterioration in the read performance as the drive fills up. The write performance does start to fall away as the drive fills but seems to stage a recovery when the drive is 90% full.

Our tested read throughput figure for the empty drive was 2,156.62MB/s which dropped to 2,142.45MB/s and 2,144.92MB/s for 25% and 50% capacity respectively. At 75% capacity, the drive staged a comeback with 2,153.04MB/s before dropping back to 2,142.79MB/s at 90% full.

The write throughput performance is much more erratic than the read as the drive fills up. The drive’s performance drops the most at 75% capacity, where it reaches 1,962.03MB/s, some 102.32MB/s slower than when the drive is empty. It stages a recovery at 90% capacity with the performance rising to 1,996.16MB/s.

We used our 4K 70/30 read/write test to see how the drive performs when handling small data as it fills up. We ran the test across all the available free space. At 90% capacity, the drive is 178MB/s slower than when fresh out of the box with a corresponding rise in latency.

To test real-life performance of a drive we use a mix of folder/file types and by using the FastCopy utility (which gives a time as well as MB/s result) we record the performance of drive reading from & writing to a 256GB Samsung SSD850 PRO.

100GB data file.
60GB iso image.
60GB Steam folder – 29,521 files.
50GB File folder – 28,523 files.
21GB 8K Movie demos.
12GB Movie folder – 24 files (mix of Blu-ray and 4K files).
11GB 4K Raw Movie Clips (8 MP4V files).
10GB Photo folder – 621 files (mix of png, raw and jpeg images).
10GB Audio folder – 1,483 files (mix of mp3 and .flac files).
5GB (1.5bn pixel) photo.
Blu-ray movie.

To get a measure of how much faster PCIe NVMe drives are than standard SATA SSD’s we use the same files but transfer to and from a 512GB Toshiba OCZ RD400.

The WD Blue SN550 handled both sets of real-life file transfer tests without any problems but dealt with the larger file sizes much more efficiently than the small files found in the 60GB Steam, 50GB File and 10GB Audio folders.

WD’s Blue range of drives covers the mainstream market segment and consists of traditional mechanical drives, as well as SATA based SSDs in both 2.5in and M.2 formats and the first NVMe based Blue drive, the M.2 SN500. Now we have the arrival of the fourth generation Blue SSD and the second NVMe Blue drive, the SN550.

The SN550 Blue is a leap forward from the SN500 Blue drive in controller, interface and choice of NAND. Unlike its predecessor which had a PCIe Gen.3 x2 interface, the new SN550 has a revamped in house WD controller with a full fat PCIe Gen3 x4 interface which obviously gives it a serious performance boost over the older drive. Not only that, the SN550 also uses the latest 96-layer SanDisk 3D TLC NAND.

The new SN550 has a larger 1TB flagship drive than the SN500 which topped out a just 500GB. The other two capacities in the range are 250GB and 500GB.

As with the SN500, the single-sided layout of the drive looks a little odd with the controller sitting on the PCB very close to the interface contacts with the single NAND package sitting on the other end of the PCB with a lot of empty space between them.

WD’s official performance figures for the 1TB SN550 are up to 2,400MB/s for Sequential reads and up to 1,950MB/s for writes. Using the ATTO benchmark we could confirm these figures with the review drive producing figures of 2,452MB/s for reads and 2,064MB/s for writes. Our own Sequential tests produced a peak read figure of 2,417.61MB/s with writes coming in at 2,079.41MB/s.

Quoted 4K random performance figures are up to 410,000 IOPS for reads and up to 405,000 IOPS IOPS for writes, both figures were obtained by running the drive at a QD of 32 with 8 threads. Using our standard QD32 4T tests the best figures we saw from the drive were 244.020 IOPS for reads and 204,873 IOPS for writes. However, a quick test using the same QD and number of threads as stated in the official figures confirmed produced a read performance of 424,903.3 IOPS with writes at 403,767.8 IOPS.

WD’s Blue SN550 may not be the fastest NVMe drive we’ve seen, but it does show the technology progress WD is making in a relatively short time frame, as its a much better performer than its predecessor, the SN500.

WD are pricing the drives at £50/£70/£125 for the 250/500/1TB versions respectively. You can get them HERE at the WD Store directly.


  • 96-Layer NAND.
  • Overall performance.
  • 5-year warranty.


  • Couldn’t match the official 4K speeds with our standard tests.

Kitguru says: WD’s SN550 Blue is an impressive drive for the mainstream market and is a marked improvement on its predecessor in both the technology used and performance gained as a result.

Become a Patron!

Check Also

Decompiled app hints at possible Google Stadia features

After decompiling the Google Stadia 2.19 APK, the team at 9to5Google have discovered a number …