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Samsung SM951 512GB M.2 PCIe SSD Review

By: Chris Ramseyer | PCIe in Storage | Posted: Jan 30, 2015 2:42 pm
TweakTown Rating: 98%Manufacturer: RamCity

Desktop Test System




We ended up using several different systems to test the SM951 to test compatibility. We ended up settling on the ASRock Z97 Extreme 6 since it has a native PCIe 3.0 x4 to an onboard M.2 socket. I also used the ASUS motherboard in the system specs above with an ASUS adapter as well as an ASUS X99 WS with the onboard M.2 connector and an adapter.


We'll publish a follow up article with all of the performance data at a later time. Choosing the right PCIe slot in your system with an adapter will be essential to getting full performance out of the SM951. We did find that in nearly every case, the M.2 socket provided the most bandwidth for this high speed SSD.



Lenovo X1 Gen 3 - Notebook Power Testing with M.2 and Windows 8.1 Pro




Our SM951 came in a very nice carbon fibre package, a Lenovo X1 Carbon Gen 3. This new notebook allows us to test SATA, AHCI and NVMe based M.2 SSDs. We'll use this system to measure notebook battery life performance on M.2 form factor devices.



Initial Performance Evaluation - 4-Corner and then Some Tests


Sequential Read




Sequential Write




Sequential 80% Read 20% Write




We added a new color to the chart today, black. The old style remains the same, QD1 in green. Like a stoplight, green means go, yellow for QD4 and red for QD10. Traces recorded on SSDs show that the drives are so fast it's difficult to ramp up high queue depths. That's where the stop light colors come from.


The new color is black, the no man's zone. This shows QD32, a nearly unobtainable depth, but the depth most companies measure and publish performance with. Samsung's document for the general availability SM951 states a sequential read performance of 2150 MB/s. We have the Lenovo model with a specific Lenovo model number and can only achieve around 1700 MB/s sequential. The Samsung document states their 2150 MB/s run is with 128KB sequential data at a queue depth of 32. We matched the setting and didn't hit that mark. We didn't just want to say we didn't hit the mark without showing a 128KB sequential test at QD32.


Now that the disclaimer has been made again, feast your eyes on that! We're getting roughly 1600 MB/s in both sequential reads and sequential writes. Our mixed workload numbers also scale really well. We've yet to test a consumer PCIe SSD that scales sequential 80/20 workloads this well.


Random Read




Random Write




Random 80% Read 20% Write




We really don't mind the lower sequential read performance because the low queue depth random read performance makes up for it and then some. The high queue depth random read performance is also higher than the spec sheet lists. In this test, the drive is hammered, so there is some level of precondition. The test also runs each scenario for a long period of time, this levels out any burst numbers. Later in the review we'll see higher random performance, but only because of initial burst performance.

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