Samsung SM951 NVMe M.2 PCIe SSD Review

By Nathan Kirsch

IOMeter Sequential Performance

Starting here in April 2015 Legit Reviews has brought ack synthetic IOMeter v1.1.0 testing to our high-end Solid-State Drive reviews as we feel that the canned benchmarks no longer show enough of the performance picture nor do they expose many of the heat issues that we are starting to encounter on M.2 PCIe SSDs. We start out testing each drive with IOMeter, but first we prepare the drive. This is done by using Parted Magic to complete a full Secure Erase each and every drive. Next we use IOMeter to prefill the drive by performing the industry standard 128KB, aligned, sequential write workload across the entire drive for a period of 20 minutes. Once the drive is conditioned we run our saved sequential test profile that runs our 128KB test for two minutes without any idle time in between the tests. The queue depth is set to 32 as we feel with NVMe drives starting to come out that we need to increase our IO depth.

iometer-seq-mbps

The 128KB Sequential Read/Write test is done primarily to make sure the drives we are testing meet or surpass the manufacturer specifications for sequential Read/Write performance. The Samsung SM951 NVMe M.2 PCIe SSD is rated at up to 2,260 MB/s sequential read and 1,600 MB/s sequential write, unfortunately Samsung doesn’t break down the speeds to the various capacities they offer. We believe the speed rating on the Samsung SM951 NVMe 256GB drive is 2260MB/s read and 1250MB/s write and we were able to top our drive out at 2,264 MB/s read and 1,245 MB/s write, which is right where we expected it to be.

iometer-seq-iops

For those that like to know the IOPS results you are looking at around 17,000 IOPS for the sequential read and 9,500 IOPS on the sequential write.

iometer-seq-time

Having high IOPs per second is generally considered good, but you also look at the latency when interpreting the results. Just because the IOPs are high it might not mean that the data is being delivered at a reasonable latency and this could cause for a poor user experience. Most enthusiasts and storage aficionados consider anything under 5ms to be good and you will end up with a good user experience. As you can see the Samsung SM951 AHCI and Samsung SM951 NVMe drives performed really similarly with identical 128KB sequential read response times of 1.85ms and 128KB sequential write times that were between 2.6 and 3.4ms.