Samsung SM951 (512GB) PCIe SSD Review
by Kristian Vättö on February 24, 2015 8:00 AM ESTThermal Throttling
In the previous pages I mentioned I have suspicions that some of the results have been affected by thermal throttling. To confirm my hypothesis, I took my datalogging multimeter and taped its thermal probe on top of the SM951's controller. Then I ran a 128KB sequential write test at queue depth of 32 and plotted the results in the graph below.
Now it's pretty clear why the performance seemed a bit low in the sequential tests. It takes less than two minutes for the drive to begin throttling itself and the performance drops to ~75MB/s. Because the SM951 is an M.2 drive, it doesn't have a chassis or heatsink to help with the heat dissipation, which combined with the fact that the SM951 is more power hungry than most SATA 6Gbps drives results in throttling issues. That said, the drive shouldn't throttle under normal usage because a continuous two-minute transfer isn't very common, but in some more IO intensive workloads with long transfers (e.g. video editing) there's a chance that performance will be affected by thermal issues.
In any case, I strongly recommend having a decent amount of airflow inside the case. My system only has two case fans (one front and one rear) and I run it with the side panels off for faster accessibility, so mine isn't an ideal setup for maximum airflow.
TRIM Validation
The move from Windows 7 to 8.1 introduced some problems with the methodology we have previously used to test TRIM functionality, so I had to come up with a new way to test. I tested a couple of different methods, but ultimately I decided to go with the easiest one that can actually be used by anyone. The software is simply called trimcheck and it was made by a developer that goes by the name CyberShadow in GitHub.
Trimcheck tests TRIM by creating a small, unique file and then deleting it. Next the program will check whether the data is still accessible by reading the raw LBA locations. If the data that is returned by the drive is all zeros, it has received the TRIM command and TRIM is functional.
In the case of the SM951, TRIM appears to be working properly.
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Makaveli - Tuesday, February 24, 2015 - link
I would love to see two Samsung 850Pro 256GB drives in Raid 0 vs this.BPB - Wednesday, February 25, 2015 - link
I was really hoping to see this compared to a RAID 0 setup. I'm considering getting one of these or a competitor's version in 2 or 3 months, but I'm also considering just getting another Samsung SSD and creating a RAID 0 setup.Flash13 - Tuesday, February 24, 2015 - link
Why trust Samsung? I don't anymore.youtard - Tuesday, February 24, 2015 - link
hurr!icrf - Tuesday, February 24, 2015 - link
Suggestion for the graphs/charts picked from a drop down: make them all have the same scale, so when flipping between them, it's easier to compare from a visual shift. Ideally, it wouldn't be a drop down, but a set of checkboxes that would show/hide each line graph on the same chart to see more than one at once. If you're pre-rendering the charts, I understand how that would be a problem.Edgar_in_Indy - Tuesday, February 24, 2015 - link
It would be a lot easier to get excited about this drive if there were real-world numbers to look at. I find it frustrating that most hard drive reviews don't show some basic load times. You know, how long to boot windows, to load a level in a game, copy a huge file, etc.It would make it much easier to judge the relative performance of drives, and decide whether the results justify the upgrade cost.
willis936 - Wednesday, February 25, 2015 - link
While it requires more technical knowledge from the reader it actually gives a lot more useful info. Time to load windows? Is that on first boot after install? After updates? After 100 programs are installed? After 10 r/w cycles? After the drive isfiles filled? With overprovisioning? I'd personally much rather synthetic tests that cover most cases so you can extrapolate subjective performance from it. You just have to know which workloads line up with which tests.DanNeely - Wednesday, February 25, 2015 - link
Page 2 of the article, section "A Word About Storage Benches and Real World Tests".TLDR version: "Too much background IO for consistent results to be possible."
Edgar_in_Indy - Wednesday, February 25, 2015 - link
From that same section: "I know some of you have criticized our benchmarks due to the lack of real world application tests, but the unfortunate truth is that it's close to impossible to build a reliable test suite that can be executed in real time. Especially if you want to test something else than just boot and application launch times, there is simply too many tasks in the background that cannot be properly controlled to guarantee valid results. "Okay, then. So a complicated real-world test is difficult to duplicate. But why can't we at least have the simple "boot and application launch times" he referenced? And what about a large file copy, like I already mentioned? That's something most people could easily relate to. And time to compress a large group of files? Etc.
If the whole idea of an SSD is to do things faster, then it would be helpful to get a stopwatch involved in these types of review, at least a little bit!
Or if it really is "Mission Impossible" to document any real world speed improvements, then I can't help but wonder if this is kind of like people paying premiums for high-performance memory, with very little real-world return.
zodiacfml - Wednesday, February 25, 2015 - link
Why not do a benchmark of a Windows installation in a virtual machine from a RAM disk?