Samsung SM951 PCIe M.2 512GB SSD Review

Mixed Workload and Steady State Testing

In the past, we could look at four-corner performance to get a good idea of how a product would act in the real world. That's no longer the case, though. Mixed-workload tests yield more useful info on what your SSD does while multitasking and running background software.

128K Sequential, 80% Read Mixed-Workload Performance

4KB Random, 80% Read Mixed-Workload Performance

The products we're testing today make this section fairly dry, but when you start looking at a larger sample size of SATA-based SSDs, the mixed-workload results get more interesting.

128KB Sequential Mixed-Workload Steady State Performance

In this test, we start out with the drives in steady state and then add sequential reads in 10% increments. Documents published by Intel suggest that consumer workloads should be measured with 80% reads and 20% writes. All drives give up performance when they're presented with mixed-data workloads, but we're looking for the product that suffers the least.

We brought in all of the PCIe-based M.2 drives we had on hand for this chart. Until the SM951, PCIe drives were actually slower than premium SATA-based products in our 80% read test. Many of the early controllers used modular designs with leftover vestiges of the SATA era. That would make them half-duplex and unable to process read and write commands at the same time. The SM951 is different; it performs exceptionally well under a mixed workload.

4KB Random Write Steady State Performance

We're looking for straight lines that show consistent performance, rather than large gaps between the highs and lows. SSDs that can serve up a stable experience are better for RAID arrays. Believe it or not, it's possible for two slower SSDs with consistent performance to outperform a pair of faster, more sporadic drives. Latency increases are compounded as the drive count in an array goes up, since one SSD has to wait on the other.

For PCIe-based M.2 products, we don't have to worry about RAID for boot arrays right now. The current rumor is that Intel will have a driver available around the release of Skylake for consumer PCIe RAID. 

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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.
  • Markor
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