The Western Digital WD Black 3D NAND SSD Review: EVO Meets Its Match
by Ganesh T S & Billy Tallis on April 5, 2018 9:45 AM EST- Posted in
- SSDs
- Storage
- Western Digital
- SanDisk
- NVMe
- Extreme Pro
- WD Black
Power Management
Real-world client storage workloads leave SSDs idle most of the time, so the active power measurements presented earlier in this review only account for a small part of what determines a drive's suitability for battery-powered use. Especially under light use, the power efficiency of a SSD is determined mostly be how well it can save power when idle.
SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.
Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.
We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled.
Like most NVMe SSDs, the WD Black has a fairly high active idle power draw—the cost of keeping a PCIe 3 x4 link active. The active idle power is a bit higher than the previous WD Black SSD but is in line with drives from Samsung, Toshiba and Phison.
Enabling all the advanced PCIe and NVMe power management features doesn't have the desired effect on the WD Black SSD. The drops by almost half, but it should have dropped by at least an order of magnitude. The original WD Black SSD used aggressive power management whether or not the operating system requested it. The new WD Black seems to be unable to save much power when used on our desktop testbed, no matter what NVMe power states are requested. We will work with Western Digital to try to isolate the cause of this poor behavior. In the meantime, the WD Black is hardly the only NVMe drive where power management has problems out of the box, but Intel and Samsung have managed to produce drives that achieve very low idle power on our testbed with little or no tuning required.
Since the WD Black is clearly unable to engage its full array of power management capabilities on our testbed, it is unsurprising to see that its wake-up latency is quite short. It is not the minimal ~15µs we usually observe from drives that aren't enabling any power savings at all, but ~230µs is still a very quick wake-up from sleep.
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Cooe - Friday, April 6, 2018 - link
This is why the 250GB 960 EVO (and inevitably for the new WD Black as well) is far and away the most popular SKU just about everywhere. At around $110-120 vs $80-90, you're only paying a premium of around 20-25% over an equivalent tiered SATA III drive (ala an 850/860 EVO), though yes, you are sacrificing your sequential write speeds past the 13GB Turbowrite cache to just 300MB/s to get that comparatively tiny price premium for good NVMe vs SATA-III ratio.Tbh though in most general consumer PC workloads the above simply isn't an issue, as sustained writes of >13GB are few & far between, and the cache turnover speed while idling is speedy quick. I think this is exactly the reason why Western Digital & SanDisk adopted the kind of handicapped nCache 2.0 into a very Turbowrite-esque system with nCache 3.0 (but more like 850 EVO's simplier static TW cache just a lot bigger, rather a dynamic one like the 960 EVO uses).
Dragonstongue - Thursday, April 5, 2018 - link
competition is good, but not if they all want to keep pricing within a few $ of each other IMO.for nvme/M.2 drives they need to make sure is more universal that it is more plug and play so consumers can be assured it will work on their motherboard as a bootable OS drive right off the bat without driver specific support (quite a few drives quite a few no matter on Intel or AMD chipset seem to have this issue hence they need more plug and play support)
costs more than a normal sata based one (performance is much higher though that does not always mean can see this difference) but having to screw around making the bios/windows able to use the drive in question sucks (not saying this is a problem with this specific model, but it is a problem)
nice write up though ^.^
PeachNCream - Thursday, April 5, 2018 - link
I agree with you on pricing. It would be good if WD had priced their drive a bit lower in order to force Samsung to respond since they have a competitive product, but they have to get a return on development costs so it's safe for them to match Samsung's price. I don't like it because the consumer isn't realizing a benefit in additional competition if neither company budges on cost, but I can understand the business justifications that are probably behind it.Cliff34 - Thursday, April 5, 2018 - link
What I do wish is that the m2 sata drives should be the same price as sata ssd. After all, the specs are the same just diff forms. Too bad for us consumers.The_Assimilator - Friday, April 6, 2018 - link
M.2 SATA drives should cost *less* than their 2.5" equivalents, and the 2.5" drives should simply be an M.2 drives in an enclosure with an M.2-to-SATA connector.Cliff34 - Saturday, April 7, 2018 - link
It should but it doesn't. My guess is because m2 form is a niche market because most computer accept SATA. Therefore, companies can charge more because they can get away with it. Unless there's a huge swing of adoption of m2 form for desktop and laptops, m2 will always cost more than SATA.zodiacfml - Friday, April 6, 2018 - link
True.wr3zzz - Thursday, April 5, 2018 - link
WD's pricing strategy is probably indicative that current demand for NVMe is still outpacing supply.Arbie - Thursday, April 5, 2018 - link
Great article and follow-up analysis of the tests; thanks.iwod - Thursday, April 5, 2018 - link
What are the difference in real world usage? We thought we needed better QD1, and even that doesn't return any significant difference in optane.