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.
Facebook
Twitter
RSS
128 Comments
View All Comments
Kristian Vättö - Sunday, March 1, 2015 - link
The 840 EVO issue takes weeks, even months to show up, so testing it is not something that we can really incorporate in our test suite.The read speed depends on the test you use and its specifications. The figures are always "up to" and tend to be based on high queue depth 128KB sequential read performance. You may want to try multiple benchmarking apps, but especially ATTO tends to show high performance since it tests multiple IO sizes.
And yes, we run the SSD as a secondary drive to eliminate any OS overhead.
MFinn3333 - Saturday, February 28, 2015 - link
Is there any way you can review the Fujitsu FSX 240GB? It's an old drive but it is the only consumer level drive that I am aware of that uses entirely SLC?Kristian Vättö - Sunday, March 1, 2015 - link
At least for now it's not in the review queue, but I will keep it in mind in case I have excess time.kenshinco - Monday, March 2, 2015 - link
How can we get the sm951 to runs up to the rated speed? The rated speed for 512gb is 2.15gbs/1550mbs read/write, but i got only 1560mbs/1570mbs read/write. I got temp monitor never pass 75 when testing.Kristian Vättö - Monday, March 2, 2015 - link
I was able to achieve 2250MB/s with 128KB sequential read (QD32) on an empty drive, which is how the read performance has been rated. That's not a realistic bench, though, because in reality you will never be reading from an empty drive.Gonemad - Thursday, March 5, 2015 - link
No word on Novachips 8TB SSD yet?http://www.theregister.co.uk/2015/03/05/eight_tera...
CallsignVega - Friday, March 6, 2015 - link
I just purchased the SM951 from the UK (512GB for $450). They are out there, you just have to know where to look.vegipiniata - Wednesday, March 11, 2015 - link
I got one SM951 512GB for 340£They were gone later that day.
Have Z97 Extreme9 and can't set it as the boot drive though :(
Bios 1.3 from DEC 2014
any chance it's the BIOS fault (too old)?
Stas - Friday, March 13, 2015 - link
There we go. Finally an incentive to upgrade from 2500k to a new platform. Once mobos with M.2 and NVM hit the market in Summer/Fall, I will be retiring the faithful rig.Edgar_in_Indy - Friday, March 13, 2015 - link
The 2500k is too good to retire!When I upgraded my main system a few weeks ago, I recycled my old 2500k and the board for use in a living room HTPC build that can handle 4K video files and do some gaming, all while running Windows Media Center with 5 ATSC tuners.