Samsung SM951 (512GB) PCIe SSD Review
by Kristian Vättö on February 24, 2015 8:00 AM ESTSequential Read Performance
Our sequential tests are conducted in the same manner as our random IO tests. Each queue depth is tested for three minutes without any idle time in between the tests and the IOs are 4K aligned similar to what you would experience in a typical desktop OS.
The sequential tests really show the benefit of PCIe 3.0 because the SM951 is approximately three times faster than a SATA 6Gbps drive and provides a ~40% upgrade over the XP941.
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The line graph does reveal some anomalies, though. First it looks like the performance scales nicely, but after queue depth of two the performance actually degrades. I'm doing some thermal throttling tests later in the article and it's very likely that the read results are affected by that because I was able to reach 2250MB/s at queue depth of 32 with a cold drive (i.e. I went straight to QD32 without doing the scaling first that heats up the drive).
Sequential Write Performance
Sequential write testing differs from random testing in the sense that the LBA span is not limited. That's because sequential IOs don't fragment the drive, so the performance will be at its peak regardless.
Sequential performance is also great, but seems to be affected by thermal throttling even more. That said, I did reach over 1500MB/s with a cold drive.
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Kristian Vättö - Wednesday, February 25, 2015 - link
I didn't test any OCZ drives for this review because the Vector 180 NDA is due in a couple of days, so stay tuned.IlikeSSD - Thursday, February 26, 2015 - link
Vertex 460A is good enough to show the difference (maybe even Arc))Shadowmaster625 - Wednesday, February 25, 2015 - link
You should clip on a simple heatsink and run the tests again.squatsh - Wednesday, February 25, 2015 - link
Based on the orientation of the drive in it's M2 slot. (Ie is the controller facing up or down) Can it be made clear if we could just put a small thermal pad and one of those tiny heatsinks (like you can get for VRMs) on the controller (assuming that is what is overheating) in order to stop the thermal throttling on desktops and laptops with enough space.Luke212 - Wednesday, February 25, 2015 - link
what happened to the Intel P3500? It's been a year and nothing.Mikemk - Wednesday, February 25, 2015 - link
Comment 100Sorry, couldn't resist
awall13 - Thursday, February 26, 2015 - link
Thanks for the great review. I like the changes in how the data is presented. One idea: In the performance consistency section, the steady-state performance could be presented with a single two-color bar per drive, with the full bar representing the average performance, and the shorter bar representing the average - 1 standard deviation. I'd still keep the second chart showing the standard deviation by itself, perhaps. Just a thought.gseguin - Thursday, February 26, 2015 - link
Performance performance performance. Ok, I get it, its fast and hard to find.Since we saw many issues crop up with the predecessors, with eventual fixes by Samsung, how much confidence is there in the drive itself from Anandtech... You know the controllers, you know the memory, you've covered different company's testing methodologies, how much confidence do you have in this product, and why is that absent from the introduction and final thoughts?
Kristian Vättö - Thursday, February 26, 2015 - link
All Samsung's issues have been related to SSD with planar TLC NAND (i.e. 840 & 840 EVO). There is absolutely no reason to believe that the SM951 shares the issues because it's based on MLC NAND and Samsung's MLC NAND based SSDs have been flawless (830 & 840 Pro).kgh00007 - Saturday, February 28, 2015 - link
Hey, nice article. I like the new SSD test suite. Is there any way to add a long term read consistency test, or any sort of read consistency test in light of the Samsung 840 EVO issues?I'm an 840 EVO user with drops in read speed to below 50Mb/s. In fact I have never gotten the advertised 500MB/s read speeds on any SSD I own. Is that because I am using them as the boot drive?
Do you test with the SSD as a second drive in the system? So taking out the overhead of the OS running on the drive as well as the test suite?
Cheers, keep up the good work, I've been learning from this site for a long time....