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 IOPS divided by 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

The SMI 2256 manages to pull off decent average IOPS under a sustained random IO workload. It can't challenge the 850 EVO that uses faster 3D V-NAND, but compared to the BX100 with SM2246EN and 16nm MLC the drop in performance isn't massive -- better yet the SMI 2256 is quite a bit faster than SanDisk's TLC drive Ultra II. 

Steady-State 4KB Random Write Consistency

Unfortunately, the performance isn't very consistent, though, but then again the SM2246EN isn't either as the BX100 is only marginally better.

SMI2256 500GB
Default
25% Over-Provisioning

The steady-state behavior of the SM2256 appears to be similar to its predecessor SM2246EN. The baseline performance is fairly low at roughly 2,000 IOPS, but bursts occur frequently and go all the way to up to 25K IOPS, although this only lasts for about a second. 

SMI2256 500GB
Default
25% Over-Provisioning
Introduction, The Drive & The Test AnandTech Storage Bench - The Destroyer
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  • Shadow7037932 - Wednesday, June 17, 2015 - link

    The benchmarks seems very lacklustre and similar to much older controllers/SSDs. I know it's still probably not optimized, but unless SSDs using this can REALLY get the price down, I don't see why people won't just go with the older SSDs like. Heck, even new SSDs like the 850 EVO can be had at a very competitive price. Reply
  • watzupken - Wednesday, June 17, 2015 - link

    Having experimented with a couple of value SSDs running the older SM2246EN controller, I feel they are not too bad for the price. For most users, I don't think they will run into much performance issues with these drives and will still enjoy a better user experience than running a mechanical drive. If you are getting a new SSD running an older controller, its likely you won't find it cheaper cause its older. Reply
  • NeatOman - Wednesday, June 17, 2015 - link

    Thats true, but paired with a i3 or anything AMD in which such a small margin when the Systems controller (like in AMD's AM3+'s 990 chipset) is the bottleneck or simply the processing power like with a i3 or lower.

    And i feel the 850 EVO 120gb at $85 is still much more expensive than a SSD you can pick up with almost the same day to day performance for $55. It's like comparing a desktop i5 to a desktop i7 IMO.
    Reply
  • Taneli - Thursday, June 18, 2015 - link

    Everything you write here is just complete garbage. Reply
  • leexgx - Saturday, June 20, 2015 - link

    i agree Reply
  • Ethos Evoss - Wednesday, July 22, 2015 - link

    the new Plextor SSD M6V has Silicon Motion SMI-2246 Reply
  • Sejong - Wednesday, June 17, 2015 - link

    TLC for everyone....this is not a welcome. :( Reply
  • SunLord - Wednesday, June 17, 2015 - link

    TLC is nice for low end low use scenarios but that about it. Reply
  • Flunk - Wednesday, June 17, 2015 - link

    This would have to be really cheap to be interesting. Reply
  • Hulk - Wednesday, June 17, 2015 - link

    My thought exactly. Reply

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