The Western Digital WD Black SN750 SSD Review: Why Fix What Isn't Broken?
by Billy Tallis on January 18, 2019 8:01 AM ESTPower Management Features
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.
For many NVMe SSDs, the closely related matter of thermal management can also be important. M.2 SSDs can concentrate a lot of power in a very small space. They may also be used in locations with high ambient temperatures and poor cooling, such as tucked under a GPU on a desktop motherboard, or in a poorly-ventilated notebook.
| WD Black SN750 NVMe Power and Thermal Management Features |
|||
| Controller | SanDisk 20-82-007011 | ||
| Firmware | 102000WD | ||
| NVMe Version |
Feature | Status | |
| 1.0 | Number of operational (active) power states | 3 | |
| 1.1 | Number of non-operational (idle) power states | 2 | |
| Autonomous Power State Transition (APST) | Supported | ||
| 1.2 | Warning Temperature | 80 °C | |
| Critical Temperature | 85 °C | ||
| 1.3 | Host Controlled Thermal Management | Supported | |
| Non-Operational Power State Permissive Mode | Not Supported | ||
The WD Black SN750 supports the typical power and thermal management features we expect from recent drives, including a reasonably high warning temperature of 80 degrees. The idle power states declare fairly quick transition times, especially for the PS3 intermediate idle.
| WD Black SN750 NVMe Power States |
|||||
| Controller | SanDisk 20-82-007011 | ||||
| Firmware | 102000WD | ||||
| Power State |
Maximum Power |
Active/Idle | Entry Latency |
Exit Latency |
|
| PS 0 | 6 W | Active | - | - | |
| PS 1 | 3.5 W | Active | - | - | |
| PS 2 | 3 W | Active | - | - | |
| PS 3 | 100 mW | Idle | 4 ms | 10 ms | |
| PS 4 | 2.5 mW | Idle | 4 ms | 45 ms | |
Note that the above tables reflect only the information provided by the drive to the OS. The power and latency numbers are often very conservative estimates, but they are what the OS uses to determine which idle states to use and how long to wait before dropping to a deeper idle state.
Idle Power Measurement
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 if supported.
The WD Black SN750 has slightly higher idle power consumption than its predecessor, both with idle states enabled and with them disabled. The SN750 is one of a few NVMe drives that cannot even come close to a reasonably deep sleep state on our desktop testbed, a problem that seems to be hard for the industry to eliminate for good.
Given the relatively poor idle power savings achieved with our desktop testbed, it's good to see the SN750's wake-up latency is so low, at under a quarter of a millisecond.
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namechamps - Friday, January 18, 2019 - link
Strangely enough I don't think anandtech has ever reviewed the 970 Pro which is likely why it isn't in the comparison. They have done the 960 pro and the 970 evo but not the 970 pro.Ryan Smith - Friday, January 18, 2019 - link
"Whatever happend to the Samsung PRO in those comparisons?"Unfortunately Samsung never sampled the 970 PRO, so we don't have it on hand. And all indications are that they're just about done with it, having never released a 2TB version (like they did the 960 PRO).
I'm really not sure if we're going to see any new consumer MLC drives in 2019. The market has bifurcated into TLC and then more boutique solutions like Z-NAND and 3D XPoint.
althaz - Friday, January 18, 2019 - link
The 512Gb drive is a ~$150 part, just buy it and test it? To many this remains the most prestigious tech site around for at least some things. SSDs have been one of those things. Not having the latest of Samsung's pro drive in your results kinda makes this whole thing not worth it, IMO.If you need an excuse do a "MLC Redux" review where you look at what was probably the faster ever MLC drive and talk about how SSD tech has changed.
eldakka - Friday, January 18, 2019 - link
" just buy it and test it?"I'm sure anandtech would be delighted to test it if you sample one to them, or donate $150 to them to purchase one with.
GreenReaper - Saturday, January 19, 2019 - link
This is the level of a business expense though. Even if you did one a day for every day of the year it would be $53,400. OK, you could get a full-time journalist for that in some places, but that assumes they are kept and not sold on or used for anything else.Solandri - Monday, January 21, 2019 - link
More troubling is that unwillingness to buy a product for review smacks of demanding bribes. "Give us a free sample or we won't review your product." Which implies that companies which shower the reviewer with gifts will get more favorable reviews.Ideally, a review site should *never* accept free samples, and do all their product reviews with samples bought from the store. That's the only way to completely eliminate any undue influence the product manufacturer may have on the product review.
Dark_wizzie - Friday, January 18, 2019 - link
I don't think they actually reviewed the 970 Pro?StevoLincolnite - Saturday, January 19, 2019 - link
Yeah. Comparisons have been a bit crap on Anandtech lately.The RTX 2080 review is lacking a good lineup of GPU's to compare with... Despite promises of "Adding more later". (Never happened sadly.)
joesiv - Friday, January 18, 2019 - link
I would love to see at least some endurance testing in anandtechs reviews. I think it's something that's missing pretty much all SSD testing I see. Yes, speed is great, but endurance is something perspective owners will care more about in the long term.NAND technology is changing over time, is it changing for the better? More layers, but often at the expense of P/E Cycles.
SSD Firmwares as well have gotten both a lot more reliable, but also a lot more complicated, with different companies doing different things to maximize performance and also endurance.
Without testing these things, we don't know if there are duds in terms of firmwares/drives that don't strike a good balance between performance/reliability.
Bare minimimum I would love to see ananadtech do the following:
- Talk to manufacturers about the actual specifications of the NAND, what is the P/E Cycle rating for the NAND. Then list it in the specs for the drives so we can do our own research/homework if we want to. This spec is very often missed in the most marketing material.
- Do a quick capture of the SMART data at the very start of the testing
- Do a capture of the SMART data at the very end of your testing.
- Check out the Block Erase Count specifically. The Average Block Erase count would give a good approximation of how much life you've used just within your benchmark suite. It's much more grainular than Percent Life Used. This SMART attribute can vary between different manufacturer/firmware/controllers, so you might need to contact the manufacturer for this info.
In the end, you'll have something like: Rated P/E count / Average Block Erase, and since your test suite is likely pretty similar between SSD's, it would be a useful metric.
Bonus points, you could also look at NAND writes (not to be confused with Host Writes), during your testing, as it's related to life expectancy and can be corrolated with Total Byte Written.
I wouldn't be surprised to see that some drives write a lot more to NAND than you are expecting, and thus have higher Average Block Erases during your testing.
At my company when I did this test, while we were evaluating a drive for our products, Tier 1 memory manufacturers and their drives, failed bitterly at this endurance test where most did fine. I attribute this to the firmware. Working with the firmware developement team, we determined that the fix would not be feasible in that generation of product, so we had to skip that product.
Specs aren't everything, we need to test it, endurance is an important aspect, and I'd love to see it represented in your reviews.
romrunning - Friday, January 18, 2019 - link
Whom do you consider to be "Tier 1 memory manufacturers" - Samsung or Intel? I can't imagine their products failing endurance tests. Or are you talking about those you would consider to be lower than Samsung - like AData, Team Group, etc. - as a Tier 2 or Tier 3?