Samsung SM951 PCIe M.2 512GB SSD Review

Four-Corner Performance Testing

Flash-based products pose more testing challenges than mechanical storage products. The workload you run before a test affects the results you see immediately after. In order to make true apples to apples comparisons between products, a strict benchmark regimen must be adhered to. With some products, the type of data used for testing, whether it's compressible or not, changes the performance story.

Test System
Processor
Intel Core i7-4790K, All Cores at 4.5GHz
Motherboard
ASRock Z87 Extreme6
Memory
Corsair Vengeance PC3-19200 (2400MT/s) 2x 8GB
System Drive
SanDisk Extreme Pro 240GB
Graphics
Intel HD Graphics 4600
Chassis
Rosewill RSV-4412R
Power Supply
Corsair 1200i 1200W
System Software and Drivers
Operating System
Windows 8.1 Pro
DirectX
DirectX 11
Drivers
Intel Rapid Storage Technology 12.9.0.1016
Microsoft AHCI

128KB Sequential Read Performance

There are only two companies with PCIe-based M.2 products on the market today: Samsung and Plextor. In the early charts, we're only showing 512GB SSDs, but later in the story we'll look at a larger group with more capacities. 

It's easy to see the performance differences between these three products, and you can expect more of the same through the rest of our review. Samsung's SM951 is easily the fastest consumer SSD on the market. It improves upon the XP941, which was last year's fastest SSD, and it's clearly quicker than Plextor's M6e and M6e Black Edition drives.

Again, Samsung's spec sheet states the SM951 512GB is capable of up to 2150 MB/s sequential reads at a queue depth of 32 using 128KB blocks. We were not able to replicate those claims with modern motherboards using the Z87, Z97 or X99 chipsets from Intel. We did, however, hit 2160 MB/s with a Z68-based motherboard. That's an old platform by today's standards, though, and we're guessing most enthusiasts are running something newer.

128KB Sequential Write Performance

Notice that we took the chart above to a queue depth of 128. Although the SATA spec only allows for queue depths up to 32, PCIe-based products can scale all the way to 256, just like the SCSI command set.

All of the tests on this page involve some degree of preconditioning, since one test acts as the conditioner for the next. To varying degrees, SSDs will demonstrate performance fluctuations based on benchmarking patterns. This is caused by the drive's wear leveling, which cleans up dirty cells and adds latency to writes.

At a more mainstream queue depth of two, the SM951 fares better than we expected based on Samsung's spec sheet.

4KB Random Read Performance

Random read performance at a queue depth of one is significant to end-user performance. We use a 10,000 IOPS rating as the way to separate great-performing SSDs from the rest of the pack. Samsung's SM951 delivers over 12,000 random read IOPS with a single outstanding command, breaking the record for consumer SSDs. 

Most desktop users don't push high queue depths because SSDs finish their work before commands start stacking up. We still run the tests to observe how a drive scales through its queue depth range. The SM951's spec sheet claims the drive is only capable of 90,000 random read IOPS, but in our tests, we achieved more than 140,000.

4KB Random Write Performance

Again, we managed to pull more performance out of the SM951 than Samsung's rates it for. When it comes to writing random data, higher queue depths are easier to achieve through multitasking. 

With this last test run, we can see the SM951 is clearly faster than the other PCIe-based M.2 products when it comes to the four corners that make up performance testing.

This thread is closed for comments
51 comments
    Your comment
  • blackmagnum
    This is an awesome upgrade for some Macbook Air/Pro users, but just wait until Intel shows their product... and will there be any hardware compatibility issues with DIY upgrades?
  • Sakkura
    I'm disappointed the promised NVMe support did not materialize. But I guess Samsung is saving that for later retail products. Can't argue with the performance though, this is by far the fastest consumer SSD around.
  • Memory Ever
    May I know the model and nae of the PCIe adapter you used in the tests???
  • JOSHSKORN
    No 1TB edition? Fail.
  • tom10167
    I wish they'd put an 840 or 850 pro in the comparison just to give us a better sense of scale. This drive is incredible, though, and $550 for a 512GB cutting edge drive is not terrible!
  • mapesdhs
    The Power Restricted Performance graph is stupid. Please stopping using
    graphs with origins that don't start at zero - the visual graphic impact is
    totally meaningless.

    Ian.
  • jeffunit
    You might want to fix the labels of your graphs. Latency in seconds? One chart shows a write speed of about 80 gigabytes per second.
  • liquidpower
    I also wished they put a 850 pro in the charts to see the jump from the fastest sata to the PCIe-based M.2
  • maestro0428
    You can purchase these at newegg.com in the Enterprise SSD section. I want one!
  • generalsheep
    Is this little bastard bootable,so i can use it as my maindrive?
  • CyranD
    I have my eye on purchasing a Sager NP8652 in the near future. Currently they list Samsung XP941 as a option. I am hoping before am ready to buy they add the Samsung SM951 as a option.

    Quote:
    Is this little bastard bootable,so i can use it as my maindrive?


    Sager let you set the Samsung XP941 as the boot drive so I assume the SM951 can be used as a boot drive.
  • Blueberries
    I would have liked to see the 850 Pro included in this as well
  • CRamseyer
    I didn't need an adapter to test this product. The ASRock Z97 Extreme6 has a M.2 x4 slot that connects directly to the CPU.

    Yes, this product is bootable. The only modern PCIe SSD that is not bootable is from Fusion-IO.
  • wolfy747400
    Any ideas why this SSD performed a little faster on some tests on a Intel Z68 Express-based motherboard than the Z97?
  • kyuuketsuki
    While the drive's performance is certainly impressive, the serving time graph shows what you really need to know: the performance will make practically no difference in the vast majority of consumer workloads. The only people who should be spending the premium for this drive are professionals who will regularly be transferring large files around. Anyone else is just wasting money, as any modern SSD will perform largely the same in practice, even if their benchmark numbers aren't as impressive.
  • damric
    I am interested in M2 since my motherboard has a slot for one. Do they work as boot drives yet? I haven't been following closely but last time I checked they did not.
  • RamCity
    Quote:
    This is an awesome upgrade for some Macbook Air/Pro users, but just wait until Intel shows their product... and will there be any hardware compatibility issues with DIY upgrades?


    Sadly neither the SM951 or XP941 are compatible upgrades in the MacBook Air or the current cylindrical Mac Pro as the standard M.2 interface connector is different from the one that Apple use. Older Mac Pro towers are fine with the use of a standard PCIe to M.2 adapter card.
  • RamCity
    Quote:
    I am interested in M2 since my motherboard has a slot for one. Do they work as boot drives yet? I haven't been following closely but last time I checked they did not.


    Most 'modern' motherboards with Z97/H97 or X99 chipsets can boot the XP941 and likely the SM951 as well, so long as your bios is up to date. Also, like Chris mentioned in the article, you'll also typically need to install windows from a USB drive.
  • CRamseyer
    Yes, they work as a boot drive.
  • damric
    1901805 said:
    Quote:
    I am interested in M2 since my motherboard has a slot for one. Do they work as boot drives yet? I haven't been following closely but last time I checked they did not.
    Most 'modern' motherboards with Z97/H97 or X99 chipsets can boot the XP941 and likely the SM951 as well, so long as your bios is up to date. Also, like Chris mentioned in the article, you'll also typically need to install windows from a USB drive.


    1888934 said:
    Yes, they work as a boot drive.


    Thanks. I might pick one up for my ASUS Z97I-PLUS.
  • bit_user
    *yawn* I just clicked for some tasty NVMe benchmarks. Should have mentioned it's AHCI-only, sooner.
  • hst101rox
    4K random reads/writes aren't any better than SATA 3 SSDs so as an OS drive I don't see an advantage. For mass storage/large files, sure.
  • CRamseyer
    This drive has the highest 4K QD1 random read from a consumer SSD available today, over 12K IOPS. It has the highest QD2 and QD4 as well. Most of us will never get beyond QD8 under normal use. The 4K random writes are really good too.

    A better metric to look at is on page 4, the mixed workload tests. You will never just read or just write data with an OS drive.
  • Markor
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