Performance Consistency

Our performance consistency test explores the extent to which a drive can reliably sustain performance during a long-duration random write test. Specifications for consumer drives typically list peak performance numbers only attainable in ideal conditions. The performance in a worst-case scenario can be drastically different as over the course of a long test drives can run out of spare area, have to start performing garbage collection, and sometimes even reach power or thermal limits.

In addition to an overall decline in performance, a long test can show patterns in how performance varies on shorter timescales. Some drives will exhibit very little variance in performance from second to second, while others will show massive drops in performance during each garbage collection cycle but otherwise maintain good performance, and others show constantly wide variance. If a drive periodically slows to hard drive levels of performance, it may feel slow to use even if its overall average performance is very high.

To maximally stress the drive's controller and force it to perform garbage collection and wear leveling, this test conducts 4kB random writes with a queue depth of 32. The drive is filled before the start of the test, and the test duration is one hour. Any spare area will be exhausted early in the test and by the end of the hour even the largest drives with the most overprovisioning will have reached a steady state. We use the last 400 seconds of the test to score the drive both on steady-state average writes per second and on its performance divided by the standard deviation.

Steady-State 4KB Random Write Performance

The WD Black has a respectable steady-state random write speed for a drive with planar TLC NAND, but the drives with 3D TLC are all faster. The Plextor M8Pe using the same controller but MLC is more than twice as fast. The SATA-based WD Blue that uses the same NAND is substantially slower despite having twice the capacity.

Steady-State 4KB Random Write Consistency

The WD Black's consistency score isn't in the gutter and is actually more than twice the Plextor M8Pe's score, but it's still far below the scores of the drives that are both fast and steady.

IOPS over time
25% Over-Provisioning

The WD Black runs out of spare area about four minutes into the test and abruptly transitions to its steady state. The performance consistency gets gradually worse over the course of the test but the average stays the same. With extra overprovisioning, the WD Black hovers around 33k IOPS with good consistency before transitioning to steady state.

Steady-State IOPS over time
25% Over-Provisioning

By the end of the test, the WD Black's steady state performance is varying from just under 1k IOPS to just over 10k IOPS. With extra overprovisioning, the WD Black is mostly staying between 10k and 30k IOPS.

Introduction AnandTech Storage Bench - The Destroyer
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  • dgingeri - Wednesday, March 8, 2017 - link

    At least they priced it about right. It's more expensive than the Intel 600p, but far less expensive than the 960 EVO and slightly less expensive than the M8Pe. This part of the market is odd. Usually, the fastest performing parts are FAR more expensive for just a small return on performance. In SSDs right now, the differences in price are fairly small, but the differences in performance are huge. I think the 960 EVO is about the best deal for a SSD, and this thing is just a shame to the "Black" label.
  • Guspaz - Wednesday, March 8, 2017 - link

    So, the product called "WD Black" is coloured blue, but there is also a "WD Blue" product? Let me guess, that one has a black PCB?
  • Gasaraki88 - Wednesday, March 8, 2017 - link

    Nope, it would have made sense if they spent the money to use a black pcb for the black drive, a blue pcb for the blue drive and the green pcb for the green drive. Nope.

    This drive gives the "Black" label a bad name anyway.
  • MrSpadge - Wednesday, March 8, 2017 - link

    They probably thought "our Black HDDs are really slow nowadays, with all those budget SSDs around, so let's call a barely-not-too-slow SSD: BLACK".
  • madspartus - Wednesday, March 8, 2017 - link

    WD Black: planar 15 nm TLC NAND

    I'll be sure to remember that WD doesn't give a shit about the quality and performance of their products and branding. Way to dilute the brand, hope the short term gains are worth it.
  • shabby - Wednesday, March 8, 2017 - link

    The branding is fine, the wd green ssd will be a qlc nand drive.
  • bug77 - Thursday, March 9, 2017 - link

    True, black has always been the performance line, it shouldn't go on any TLC parts. Not even on 3D TLC.
  • romrunning - Wednesday, March 8, 2017 - link

    On your Storage Bench - Light (Latency) graph, you show the Intel 750 and Patriot Hellfire on top despite the Samsung drives beating them both in "Full" condition. So if they tie on the empty drive score, the Samsungs should be on top due to their full drive latency.
  • Gasaraki88 - Wednesday, March 8, 2017 - link

    How come you didn't test any drives that use the Phison E7 controllers? Patriot Hellfire, MyDigitalSSD BPX, and Corsair Force?
  • BrokenCrayons - Wednesday, March 8, 2017 - link

    This certainly isn't an impressive product.

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