Samsung SM951-NVMe (256GB) PCIe SSD Review
by Kristian Vättö on June 25, 2015 9:40 AM ESTRandom Read Performance
For full details of how we conduct our Iometer tests, please refer to this article.
This is the graph I've been dying to see ever since I first heard about NVMe. Random read performance at low queue depths was mostly bottlenecked by AHCI latency because at QD1 the controller can only read from one NAND die (it's asked to read one 4KB chunk of data at a time), meaning that a tremendous share of the latency was caused by the command overhead. As the NVMe command set is much simpler and the whole IO stack is lighter, it opens the doors for improved low queue depth performance, which is exactly what we are seeing with the SM951 NVMe.
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At QD1 the SM951 NVMe offers about 50MB/s, whereas the best AHCI drives I've seen hover around 30-35MB/s, resulting in about 50% gains. Performance at QD2 and QD4 is also better than what other drives offer and in general the SM951 NVMe has excellent random read performance including the high QDs as well.
Random Write Performance
NVMe doesn't present similar gains to random write performance, though. This is an area where Intel clearly has an advantage, but given that the SSD 750 carries an 18-channel controller that is hardly a surprise. Moreover, because the SSD 750 features full power loss protection Intel can cache more user data in the DRAM buffer without the risk of data loss, which can further improve random write performance as IOs can be combined more efficiently. Intel's custom driver may also help with random write performance because the native Microsoft driver has some write performance issues due to Force Unit Access (basically FUA won't consider write to be complete until it has been written to its final medium i.e. NAND, whereas Intel's driver can consider write to be complete when it reaches the DRAM buffer).
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bigbrainz - Wednesday, September 16, 2015 - link
So which would be best for video editing (not rendering--the editing/preview stage)? The 750 or the SM951 (AHCI since the NVMe isn't really available yet)? Generally that would mean playing back one video stream, although with compositing it can briefly get to 2 at a time. Rarely more than that though (for my videos). I'm not really sure if that would be considered random or sequential or light or heavy or what?THANKS!!!!
metaxis - Wednesday, October 28, 2015 - link
It's really unfortunate how much these performance line graphs squander the benchmark data you've gathered.* One device at time prevents visual comparisons.
* One graph from a series at a time means a ton of toggling back an forth, or opening a lot of windows
* ...but, because the scale isn't fixed, you *still* can't visually compare them.
The graphs are pretty terrible over at /bench too.
* no horizontal scale labels
* product/comparison mixes "less is better" and "more is better" with abandon
* you have to hunt around a ton to actually get anything useful
* choose *either* 2 devices and all the shared benchmarks *or* all devices that happen to have been tested under a single benchmark
* links to product reviews mostly gone
These are some of the weakest visualizations of this valuable set of data I can imagine, and it makes me sad.
dtscaps - Friday, March 11, 2016 - link
Ok, this is supposed to be a review to guide me what SSD to buy. I read 10 pages of performance specs and 72 more comments dealing with microseconds marginality. The fact that this drive does or does not have an AES self encrypting mechanism adering to OPAL 2 with a possible IEEE1667 extension IS IMPORTANT. IT IS A COMPLETE SHOW STOPPER if the drive cannot encrypt data. Maybe except if you are a kid playing with new toys.So, is this SSD self encrypting ?
Does it support Opal 2
Does it support the IEEE1667 extension?
Chris023 - Monday, April 25, 2016 - link
Just a little FYI for anyone that runs across this article. I just purchased the Samsung 950 pro boxed consumer version in 512GB. I Installed it with an adapter card in an old Asus M4a88TD-V EVO/USB3 motherboard. To my amazement the bios recognized and even put it in the boot sequence. I already had an 830 SSD. I booted up with the old SSD 830 and initialized this new 950. Then using Samsung's transfer software cloned the 830 to the 950. Rebooted, turned the 830 to disabled in the boot order, and enabled the 950 as the boot drive. It took two tries for me to realize I had to disable the 830 in the boot menu as the bios automatically looked for a bootable AHCI drive first. I have now been booting and running the 950 Pro for over a week with no issues. This is on an old AMD 880 chipset!!! This is a PCIe 2.0 MB! Even so it still manages to outperform the older Samsung 830 SSD enough to notice. User Bench shows my SSD performance going from 70% to 169% of average. Average will shoot up much higher once I get a true PCIe MB with native NVMe drive support.