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Western Digital Black SN750 SSD Review (Page 2)

By Chris Ramseyer from Jan 29, 2019 @ 19:25 CST
TweakTown Rating: 91%Manufacturer: Western Digital

1TB Class Performance Testing

Product Comparison


The charts show all of the next generation 1TB NVMe SSDs shipping today. The 2019 releases include the new WD Black SN750, ADATA SX8200 Pro, HP EX950 and the MyDigitalSSD BPX Pro that came to market at the tail end of 2018.

In the last couple of reviews, we've looked for the SanDisk Extreme Pro and WD Black (the previous generation) but had a difficult finding the drives. That indicated to use a new model was coming in the near future. We used the SanDisk Extreme Pro in the charts, but the performance is identical to the previous generation Black. We rounded out the charts with the Plextor M9Pe add-in card, Samsung 970 EVO, and 970 Pro. We updated all pricing 24 hours before publishing the review.

Sequential Read Performance


The 1TB Black SN750 brings with it the same dip at queue depth 2 (QD2) that we observed on the previous generation as well as the products using the Phison E12 controller. We massaged the test a bit to get a better result much as we did with the MyDigitalSSD BPX Pro, but we couldn't make it go away completely with our test script. Instead of focusing on the QD2 sequential read performance here, we will focus on performance in the sequential mixed workload test towards the bottom of this page.

Sequential Write Performance


The sequential burst write performance with the new Black SN750 is more consistent compared to the previous model from WD. The QD1 performance is a little higher but the QD2 performance is nearly identical.

Sustained Sequential Write Performance


Moving past the burst sequential writes, here we see a long 128KB write to the entire user area of the SSD. The 1TB Black SN750 burst speed is slightly higher than the previous generation, and the sustained write speed is higher as well. We observed some severe dips starting around 45% of the way through the test. This is after nearly 500GB of data written to the drive without a break, so we don't have any real concerns about this affecting users.

The data "folding" from the SLC to the TLC area likely causes the dips. Some companies choose to fill the SLC area and then write data directly to the TLC, but the Black SN750 moves all data to the SLC first. When the data moves to TLC, it causes a small performance dip during the process.

The dips could also be the result of thermal throttling. The SN750 with a heat sink, set to arrive in a month or so, will let us know for sure. Both folding data and thermal throttling can appear the same in extended write tests precisely like this.

Random Read Performance


The all-important random read test....where to start. For the last few weeks, we've talked about the incredible low queue depth random read performance from drives with Micron's 64L TLC and Silicon Motion controllers. WD uses SMI controllers for some downmarket products, but the flagship Black series uses an in-house controller.

The new Black with the 2019 optimizations scores 10,725 IOPS at QD1, around 575 IOPS more than the previous generation in our testing. Using Anvil Disk, we scored just over 12,000 random read IOPSs at QD1, but the other drives also score higher in that test due to the sequence we run.

The important takeaway from the random read test is that the new Black SN750 is only slightly faster than the previous generation in this particular area and not much quicker than the best SATA SSDs shipping today like the Crucial MX500. This will carry over to many of the applications tests on the next page and in the user experience; you will feel at home with this drive.

Random Write Performance


The Black SN750 does perform very well with small block size random data writes. The drive is faster at low queue depths compared to the other modern drives in the charts today. These are burst tests absorbed by the SLC buffer and not sustained writes where the data folds into the TLC area.

70% Read Sequential Performance


We have to rely on the mixed workload test to get a better understanding of the low queue depth sequential read performance due to the odd error we get with some next-generation NVMe controllers running 100% reads.

The new 1TB Black SN750 scores lower than the previous generation drive at QD2 but quickly joins the Extreme Pro NVMe with a similar slope through the higher queue depths in this test using 128 KB blocks and a 70% read.

70% Read Random Performance


In the random mixed workload test, we see a slightly higher performance reading from QD2 to QD8. The new 1TB Black SN750 starts to leap ahead of the previous generation NVMe drive from WD/SanDisk between QD8 and QD16. The new drive continues its lead with a single worker through the rest of the test.

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