Performance Consistency

We've been looking at performance consistency since the Intel SSD DC S3700 review in late 2012 and it has become one of the cornerstones of our SSD reviews. Back in the days many SSD vendors were only focusing on high peak performance, which unfortunately came at the cost of sustained performance. In other words, the drives would push high IOPS in certain synthetic scenarios to provide nice marketing numbers, but as soon as you pushed the drive for more than a few minutes you could easily run into hiccups caused by poor performance consistency. 

Once we started exploring IO consistency, nearly all SSD manufacturers made a move to improve consistency and for the 2015 suite, I haven't made any significant changes to the methodology we use to test IO consistency. The biggest change is the move from VDBench to Iometer 1.1.0 as the benchmarking software and I've also extended the test from 2000 seconds to a full hour to ensure that all drives hit steady-state during the test.

For better readability, I now provide bar graphs with the first one being an average IOPS of the last 400 seconds and the second graph displaying the standard deviation during the same period. Average IOPS provides a quick look into overall performance, but it can easily hide bad consistency, so looking at standard deviation is necessary for a complete look into consistency.

I'm still providing the same scatter graphs too, of course. However, I decided to dump the logarithmic graphs and go linear-only since logarithmic graphs aren't as accurate and can be hard to interpret for those who aren't familiar with them. I provide two graphs: one that includes the whole duration of the test and another that focuses on the last 400 seconds of the test to get a better scope into steady-state performance.

Steady-State 4KB Random Write Performance

Given the higher over-provisioning and an enterprise-oriented controller, it's no surprise that the SSD 750 has excellent steady-state random write performance. 

Steady-State 4KB Random Write Consistency

The consistency is also very good, although the SSD 750 can't beat the 850 Pro if just focusing on consistency. When considering that the SSD 750 provides nearly three times the performance, it's clear that the SSD 750 is better out of the two. 

Intel SSD 750 1.2TB (PCIe 3.0 x4 - NVMe)

At the initial cliff the performance drops to around 15K IOPS, but it quickly rises and seems to even out at about 22-23K IOPS. It actually takes nearly an hour for the SSD 750 to reach steady-state, which isn't uncommon for such a large drive but it's still notable. 

I couldn't run tests with added over-provisioning because NVMe drives don't support the usual ATA commands that I use to limit the LBA of the drive. There is similar command set for NVMe as well, but I'm still trying to figure out how to use them as there's isn't too much public info about NVMe tools.

Intel SSD 750 1.2TB (PCIe 3.0 x4 - NVMe)
Introduction, The Drive & The Test AnandTech Storage Bench - The Destroyer
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  • Per Hansson - Saturday, April 4, 2015 - link

    It's most likely due to the poor performance of file transfers below 4KB with this drive.
  • Shadowmaster625 - Thursday, April 2, 2015 - link

    The funny thing is that the X25-M is STILL a great product. You can buy one on ebay and place it into a new build and it works just fine. And will continue to work just fine for many more years.
  • eanazag - Thursday, April 2, 2015 - link

    I have 4 X25-M 80 GB drives in RAID 0. The 750 is cheaper and faster than my setup. Price is based on what I paid several years ago for them.

    I would need a new motherboard and CPU to make this drive bootable. I do want.

    Intel's PCIe lane bottleneck is pathetic. It seems to be a constant concern. X99 and Haswell-E is not the best answer to the problem. I am really skeptical about waiting for Skylake and the associated chipset. Broadwell for desktop hasn't even been released yet. Skylake for desktop will likely be next year at this rate.
  • DanNeely - Thursday, April 2, 2015 - link

    Intel's never waivered from stating that SkyLake will launch on time and that all of the 14nm ramping delays will be absorbed by shortening broadwell's life. At this point I am wondering if desktop broadwell might end up being cut entirely in the mainstream market segment; with only the LGA2011 variant and possibly the LGA1150 celeron/pentium class chips that normally launch about a year after the rest of the product line on the desktop.
  • r3loaded - Friday, April 3, 2015 - link

    Skylake will bring 20 PCIe 3.0 lanes on the PCH, in addition to the PCIe 3.0 lanes coming off the CPU (Skylake-E CPUs will introduce PCIe 4.0) as well as support for up to three SATA Express/M.2 devices. Don't worry, Intel is well aware of the bandwidth bottleneck and they're addressing it.
  • Hung_Low - Thursday, April 2, 2015 - link

    So is thisi 750 the long rumoured P3500?
  • Shadowmaster625 - Thursday, April 2, 2015 - link

    I'm not satisfied with the explanations of why this product is slower than the SM951. By all rights it should be faster. Why would it still get a recommendation by anandtech?
  • Kristian Vättö - Thursday, April 2, 2015 - link

    It's only slower in the Heavy and Light traces, which focus more on peak performance rather than consistency. In The Destroyer trace the SSD 750 has significantly lower IO latency and that's what's critical for power users and professionals since it translates to more responsive system. The Heavy and Light traces don't really illustrate the workloads where the SSD 750 is aimed for, hence the SM951 is faster in those.
  • BD2003 - Thursday, April 2, 2015 - link

    Is it really measureably more responsive though? I guess I have a hard time believing that latencies measured in microseconds are going to bare out into any real world difference. Maybe it makes a difference on the single digit millisecond scale, but I'm talking real world here. Like is there any scenario where you'd be able to measure the *actual responsiveness*, meaning the time between clicking something and it actually responding to your command is measurably better? Even if it's just something minor like notepad opens in 50ms vs 100ms while you're compiling and backing up at the same time?

    Their target market is consumers so I feel like they've got to justify it on the basis of real world usage, not theory or benchmarks. From what I'm seeing here the SM951 looks like a better buy in every single way that matters.
  • SirPerro - Monday, April 6, 2015 - link

    It's not about "clicking and responding". It's about different servers/databases handling hundreds of requests per second in a heavily multithreaded scenario.

    For UI interaction you probably cannot make the difference between this and the cheapest SSD on the market unless compared side by side.

    As the review explains, this is targeted to a very specific niche. Whether people understand the scope of that niche or not is a different thing.

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