Samsung SM951 PCIe M.2 512GB SSD Review

Final Thoughts

The SSD market will change in 2015. Marvell, SandForce (now part of Seagate), Phison and JMicron will release PCIe-based controllers around June, just in time for Computex. We expect Intel to release the HHHL 750-series SSD, the company's first consumer PCIe-based SSD, any time now. At least two vendors will even break the PCIe market into two categories, performance and value, similar to the 2.5" SATA SSDs today. The dividing line will be the number of PCIe lanes utilized. Expect value-oriented products to sit on two lanes, while high-end offerings exploit four.

Samsung's SM951 ascends the throne in that latter category as the fastest consumer SSD you can buy. How long it holds the title remains to be seen. Not only are other companies working to take the crown, but Samsung's retail arm might have a solution of its own.

Samsung chose to release this product to OEMs with 16nm 2D planar flash, a cost-cutting measure. System builders work hard to keep costs low at the component level, and 3D V-NAND would have been counterproductive on an already expensive device. We expect Samsung to take advantage of its PCIe development advantage and deliver a retail product aimed at enthusiasts with second- or third-generation 3D V-NAND. The SM951 press release alluded to an upcoming NVMe-based offering later in 2015. We found that little quip extremely odd; it was almost like a warning to early adopters.

Until Samsung announces a PCIe-based M.2 SSD for the retail market, we'll have to keep searching out hard-to-get gems like the XP941 and SM951, which ride a fine line between the retail and gray markets. Sadly, that means these specialty products cost more than other premium SSDs made in larger quantities. You'll also have a difficult time finding them for sale.

Most new premium motherboards already support M.2 PCIe SSDs. On those that don't, you can use a M.2-to-PCIe adapter, just like plugging in a video card. The adapters are passive; just be sure to get the right model built for PCIe M.2 products. Notebook support is more complicated. The Lenovo X1 Carbon Gen 3 supports the SM951, as does at least one Dell model that is shipping today. Several companies plan to launch notebooks with support for four-lane M.2 drives, and some of those won't even accommodate 2.5" SATA storage devices. Undoubtedly, this will increase M.2 market share.

At this time, Samsung's SM951 is the fastest M.2 product you can buy. Not only is it quicker than existing PCIe-based M.2 drives, but it also delivers performance that compares to all-in-one RAID products like OCZ's RevoDrive and G.Skill's Phoenix Blade. Our testing didn't uncover any weak links in performance. Generally, it's difficult for a company to develop a SSD that doesn't have a flaw somewhere. But Samsung's new UBX controller manages to fix the XP941's weak mixed-workload performance and heat issues under random write workloads. The SM951 runs much cooler, so it won't be a problem running the drive on your motherboard with a video card close by.

The SM951 512GB is the best consumer SSD money can buy. We just wish Samsung would release a 1TB version and improve availability.

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51 comments
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  • 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.
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