How We Test PCIe 4.0 Storage: The AnandTech 2021 SSD Benchmark Suite
by Billy Tallis on February 1, 2021 1:15 PM ESTPower Management
Idle power management for SSDs can be surprisingly complicated, especially for NVMe drives. But it is also vitally important for any battery-powered system. Real-world client storage workloads leave SSDs idle most of the time, so idle behavior is a big factor in how battery-friendly a drive is. Power draw when idle isn't the only thing that matters; how quickly a drive can enter or wake up from a low-power state can have a big impact on how effective its power management is.
For SATA SSDs, the host system doesn't have a lot of say in how the drive manages power. Using the SATA Aggressive Link Power Management (ALPM) feature to mostly power the SATA connection is usually sufficient to put a drive to sleep. But the lowest-power sleep state supported by SATA devices (DevSleep) requires extra signalling on a pin that's part of the SATA power connector. This means that DevSleep is in practice only supported on laptops, and our desktop testbeds cannot use or measure this sleep state.
NVMe includes numerous features pertaining to power management or thermal management. Most of them are optional in the NVMe spec, but there's a common subset supported by most consumer SSDs. NVMe drives can support numerous different power states, including multiple active and multiple inactive power states. The drive's firmware provides information about its capabilities to the host system:
| Samsung 980 PRO NVMe Power States |
|||||
| Controller | Samsung Elpis | ||||
| Firmware | 1B2QGXA7 | ||||
| Power State |
Maximum Power |
Active/Idle | Entry Latency |
Exit Latency |
|
| PS 0 | 8.49 W | Active | - | - | |
| PS 1 | 4.48 W | Active | - | 0.2 ms | |
| PS 2 | 3.18 W | Active | - | 1.0 ms | |
| PS 3 | 40 mW | Idle | 2.0 ms | 1.2 ms | |
| PS 4 | 5 mW | Idle | 0.5 ms | 9.5 ms | |
When a drive and the host OS both support the Autonomous Power State Transition (APST) feature in NMVe 1.1 or later, the host system can give the drive a set of rules for how long it should wait while idle before dropping down to a lower-power state. Operating systems choose these delays based on the power state entry and exit latencies claimed by the drive, and other configuration information about the system's overall tolerance for increased disk access times.
One common problem with the NVMe APST feature is that the NVMe spec doesn't really say anything about how APST interacts with PCIe Active State Power Management. SSD vendors tend to make assumptions that eg. a system which configures the drive to use its deepest idle state will fully support PCIe APSM. Most of the time, things work out, but it's also possible to end up with a drive that goes to sleep and never wakes up, or a drive that defaults back to its highest power state if anything goes wrong when it tries to go to sleep.
Using our Coffee Lake testbed that has fully functional PCIe power management, we test SSD power in three states. Active idle is when the drive is not using any externally-configurable power management features: SATA or PCIe link power management is disabled, and NVMe APST is off. We're now using a more reliable and broadly-compatible method for disabling APST through the Linux kernel rather than directly poking the drive's registers. This means that some drives will probably end up showing higher active idle power draw than we have previously measured.
Even though there are many combinations of power management settings and power states that can be used with a typical consumer NVMe SSD, we condense it down to just two low-power configurations to test. What we call "Desktop Idle" is using the features that are almost always available and working on desktop platforms, even if they're off by default. This includes enabling SATA ALPM, NVMe APST, and PCIe ASPM.
Next, we have the "Laptop Idle" state, with all the power-saving features fully enabled. For SATA SSDs, this would include DevSleep, so we can't fairly measure the Laptop Idle power draw of SSDs. For NVMe SSDs, this includes enabling PCIe L1 substates.
Accurately measuring the time it takes for a drive to enter a low-power state is tricky, but measuring the time taken to wake up is straightforward. We run a synthetic test that performs a single 4kB random read once every 10 seconds. When power management features are disabled and the drive stays in its active idle state, the random read latency will be determined mainly by the speed of the NAND flash. When the drive is in the Desktop Idle or Laptop Idle state, it will go to sleep between each random read, so we can repeatedly sample the time taken to wake up and perform a random read. The difference between this time and the random read latency from the drive in the active idle state is due almost entirely to the overhead of waking up the drive from a sleep state, and this difference is what we report as a drive's wake-up latency.
Conclusions
In this article we hope we've given you an insight into how much goes into testing a modern solid state storage drive - something more than just running CrystalDiskMark and finding peak sequential speeds! The new suite is not only more in-depth, but also we've streamlined it somewhat for automation, enabling fewer sleepless nights as deadlines loom on the horizon (or put another way, more reviews to come). We're obviously keen to take on additional feedback with the testing, so please leave a comment below.
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nobozos - Tuesday, February 2, 2021 - link
One thing that bothers me about benchmarks in general is that they often don't show the statistics normalized against the cost of the thing being measured. For example, I'd like to see iops/$, or GBs/$, or ???/$ in all your tables and charts. I think you've sometime done this in the past, but it should become a regular feature of every review.kepstin - Tuesday, February 2, 2021 - link
Prices are so volatile in the market (and sometimes even regional) that a static number here doesn't make sense imo. The periodic roundups of recommended drives do take price and performance into account.KarlKastor - Tuesday, February 2, 2021 - link
@BillyThank you for the detailed test and the explanation of each procedure.
There is one thing that I am missing in this test. How does a drive perform in heavy and light, if it is 80 or 90% full?
Is it closer to a fresh drive or closer to full drive?
Maybe you can run a drive in that precondition. Not as a general test, but just once to show how a drive behaves.
Oxford Guy - Tuesday, February 2, 2021 - link
Great article. I particularly agree with the use of 80% full because that's a lot more realistic than empty drive testing. In fact, I would skip empty drive testing and stick with 60% and 80% full tests.• Having three Samsung drives out of nine shown seems like an ad for Samsung, even if that wasn't the intention. That Samsung is a popular brand is not a good reason. OCZ used to be popular and the company's bad practices caught up with it.
• Please test the Inland brand drives. People can find Samsung drive tests all over the Internet. I'm not saying don't test them, of course. I am asking that you provide significantly more added value to your SSD reviews by reviewing drives almost no one else reviews. For instance, I recently purchased the 2 TB Inland Performance Plus drive, which uses the Phison E18 controller. It should provide very good performance but reviews would help.
Another issue with brands like Inland is firmware updates. Sandforce, the most infamously poor-quality SSD controller outfit, finally (they claimed) fixed a serious bug in their second-generation controller years ago and OCZ released yet another firmware update. Yet, other brands were sold using the controller and the OCZ tool wouldn't recognize them so they could be patched. Sandforce, of course, never bothered to provide a utility for patching these other brands' drives.
This issue isn't so severe if the consumer just happened to have purchased a Sandforce drive from a vendor that sometimes makes the effort to create patches, like Intel. But, it's really inexcusable to have such a caveat emptor attitude that one doesn't make a strong effort to warn consumers about any risks involved in buying drives from less dominant brands. Phison, for instance, has reportedly been working on improving the firmware for the E18. Will Inland ever receive a patch? I haven't looked much into it but when I did a a few cursory searches about Inland and firmware patches over the years it seemed that it was the typical "off brand" situation — where the drives are stuck forever with their initial firmware.
That's not such a severe problem if the firmware is decent to begin with (unlike OCZ, which, despite dozens of updates never fixed the Vertex 2 drive at all) — but it's something Anandtech should be and should have been raising awareness about. Your site covered OCZ's bait and switch tactics (when it switched 32-bit NAND in the Vertex 2 for 64-bit NAND, causing the drives to brick randomly — especially when put to sleep), which was great.
But, unless I missed it I haven't seen any articles about the drawbacks of purchasing SSDs from smaller brands. And, why not put some pressure on the industry to stop enabling companies like Sandforce to not provide utilities to patch their drives (and utilities to un-brick them when they go into 'panic mode'). It was completely inexcusable — the industry silence around that. Sandforce made it much more important to brick the drive when there was a software glitch, no matter how minor, apparently to 'protect its IP'. Shouldn't the consumer's data be considered the priority? Well, they came out with a not-at-all-conflict-of-interest partnership with DriveSavers. That's right — you get the joy of a drive that will brick at any moment and then you can spend thousands to 'protect the vaunted Sandforce IP' and pad its pockets and DriveSavers'.
The tech press is supposed to protect us from caveat emptor. So, please... start reviewing smaller brands, start providing a bigger picture than the latest from Samsung, and put more pressure on industry players (like Inland) to do the right things, like keeping their drives' firmware current.
Oxford Guy - Tuesday, February 2, 2021 - link
Speaking of bad practices, let's take a look at Samsung.1. The company breaks industry convention and intentionally confuses consumers by labeling QLC drives "MLC", and TLC drives as well. That's an example of fraud which is, unfortunately, legal.
There should have been an article from every tech site condemning this. I don't recall seeing even one. You know, it's not too late, either!
2. The company posted fantasy power consumption figures for drives like the 830 and the tech press and companies like Newegg dutifully posted those specs. Samsung sold a lot of drives based on word of mouth — about how amazingly efficient its drives were, based on those nonsensical power usage claims.
3. The company released its planar TLC drives in such an under-engineered (half-baked) state that they had to be kludged into frequently rewriting stored data to keep their performance somewhat acceptable. The steady state performance of the 128 GB 840 drive earned particular, fully justified, scorn from HardOCP.
Kristian Vättö - Tuesday, February 2, 2021 - link
All SSDs with a Phison controllers are the same - designed and assembled by Phison. Sure, there are some FW differences as every customer can request customisations, but at a high-level an SSD with a Phison controller is a Phison SSD. None of the small brands produce their own SSDs, they simply work with Phison and other similar ODMs who offer turnkey solutions. Anyone can start their own brand if they have enough capital to meet the MOQ requirements.It was different 10 years ago when there were numerous incumbent controller and SSD vendors shipping new designs every 6-12 months ago. At that time, it was never sure what to expect and at AT we were more or less a validation partner even. Nowadays there are a few large factories pumping out stuff with different labels.
Oxford Guy - Tuesday, February 2, 2021 - link
The Sandforce 2200 controller was used by a bunch of different companies but to my knowledge it’s not possible to patch that bug if one owns one of the smaller brands’ drives. It’s unlikely enough to get OCZ’ utility to recognize its own drives, let alone another vendor’s.So, even if the controller is the same and even if the other hardware is standard, is there a standard utility that can be used with any drive made by any brand? Sandforce never seemed to bother to offer anything like that and there were a lot of different brands using its controllers.
Also, even when a controller is standard the firmware may not be, as in the case of Intel’s Sandforce drives as far as I know.
Oxford Guy - Tuesday, February 2, 2021 - link
So my question remains: are all the Inland drives able to be firmware-updated and secure erased?Or, are such ‘small brand’ drives locked out of those things?
rahvin - Tuesday, February 2, 2021 - link
Why would they offer a tool when they can charge the OEM to produce a branded tool for those drives only?There's little incentive for an ODM to provide anything they aren't paid for and their customers aren't the retail buyers, it's the OEM's.
Billy Tallis - Tuesday, February 2, 2021 - link
Samsung's over-represented in this article mainly because they're one of the few companies still sampling new SATA drives for review, and I didn't want to have the SATA market segments represented by old 64-layer drives that you can no longer purchase.As for the Inland drives: I don't have any easy way to get samples of a large number of their drives. I strongly prefer not wasting time re-testing the same drive with a different brand's sticker. I do plan to soon have full results for E12+TLC, E12S+QLC, E16+TLC, E16+QLC drives in Bench, and I'll be getting an E18 sample soon. They won't all be from the same brand, but the results will be generally representative of the equivalents from other Phison-based brands.
I also wish the smaller SSD brands did a better job of making firmware updates available. That is definitely a valid reason for preferring some brands over others. It's a little hard to evaluate vendors on the timeliness of their firmware update releases at product launch, and I've never made it a priority to systematically compare vendors on this post-launch.
Part of why it's been a low priority has been because it seems like firmware updates are generally not as important these days. When a controller is first launched there are often a few updates to optimize performance, but those usually don't have a big impact on the overall standings of a drive. Firmware updates to fix critical bugs seem to be thankfully less common. And for users who really do care about making sure they've got the absolute latest firmware on their Phison drives, you can usually find a way to apply the update using a different vendor's tool—not ideal by any means, but it works.