TEMPERATURE VS THROUGHPUT
In order to test out the SM951’s heat output we used Iometer. We set 128KB seq. read and write workloads at QD32 to get the most heat and speed possible out of the drive over a 5 minute span, displayed are the speeds every second (300 points). With a temperature probe we recorded the temperature of the controller every 30 seconds over the 5 minutes.
If you have seen our review of the 512GB AHCI variant, you may ask yourself why we only tested 5 minutes here. The answer is quite simple, after 300 seconds of writing at 1.2GB/s, the total amount written exceeds the actual capacity of the 256GB SSD. It is pointless to continuously write after the point of fill. So, as you can see here, the 256GB SM951 NVMe SSD still gets up to about 80C after two minutes, or 120GB of continuous writes at full speed. Reads are a bit lower maxing out at 76C. We notice that there is no write drop off which we experienced with the AHCI variant, which is great to see as well.
REPORT ANALYSIS AND FINAL THOUGHTS
There you have it, NVMe really does deliver better performance than AHCI! In all benchmarks, it was faster in one way or another. Read speeds peaked out at 2.26GB/s and writes at 1.28GB/s. We saw it reach nearly 300K IOPS read and hit just about 100K IOPS write as well.
One of the biggest advantages of NVMe is lower latency. When looking at the average response time with Iometer under the same 4K random QD32 workloads, the NVMe variant of the SM951 has about 50% less latency overall. This also continued to show improvement in PCMark Vantage where it reached 187K points. In PCMark 8’s consistency testing we saw very good performance as well. Consistency proved to be very good in this SSD. Through each phase in this test its performance remained constant, it did, however, take a little bit to recover from the heavy workload phase. It delivered the highest bandwidth out of all our testing so far and had about 20% lower latency than the AHCI variant, which translates to better performance during real-world type workloads.
Now for thermal performance, we want to elaborate on what the results actually mean. These temperatures are very unlikely to be reached in real-world use, just as are the insanely high read IOPS. These are worse case scenarios where we are reading and writing to the SSD’s full capacity at its full speed. People often read these results and expect their drive to hit these temperatures under normal consumer usage, however, this isn’t true. Unless you have another high-speed storage device that allows for this SSD to reach full bandwidth in reads and/or writes, the SM951 is not going to hit 70-80C. Most people who buy this SSD will be transferring at the limits of a single SATA 6Gb/s SSD and more often than not, at most two in RAID 0 @ 1GB/s. So for the majority of people out there who will have these SSDs, you don’t need to worry about the heat output. For the few who can and will saturate its performance though, look into adding a fan near this SSD or a small RAM heatsink or thermal pad. With just a 120mm fan pointed at it during testing the SM951’s controller stayed under 62C.
Big things really do come in small packages. At the end of the day, would we recommend this NVMe variant over the AHCI one? Yes we would…as long as you can find one and your system is compatible that is. This is the first M.2 PCIe NVMe SSD out and it isn’t really meant for consumers as it is an OEM product. As you read we even had issues with it in our other X99 test bench, so be warned. Please check with your motherboard/system manufacturer to verify compatibility before purchase. Otherwise, it is a safer bet to go with the AHCI variant.
The SM951 M.2 PCIe NVMe SSD is tiny, fast, and energy-efficient. For its great performance we award it our Gold Seal! If you have a high-end system and want to get the most out of it, the SM951 is a great choice whether it be the AHCI or NVMe variant tested today.