Performance Consistency

Performance consistency tells us a lot about the architecture of these SSDs and how they handle internal defragmentation. The reason we don’t have consistent IO latency with SSD is because inevitably all controllers have to do some amount of defragmentation or garbage collection in order to continue operating at high speeds. When and how an SSD decides to run its defrag or cleanup routines directly impacts the user experience as inconsistent performance results in application slowdowns.

To test IO consistency, we fill a secure erased SSD with sequential data to ensure that all user accessible LBAs have data associated with them. Next we kick off a 4KB random write workload across all LBAs at a queue depth of 32 using incompressible data. The test is run for just over half an hour and we record instantaneous IOPS every second.

We are also testing drives with added over-provisioning by limiting the LBA range. This gives us a look into the drive’s behavior with varying levels of empty space, which is frankly a more realistic approach for client workloads.

Each of the three graphs has its own purpose. The first one is of the whole duration of the test in log scale. The second and third one zoom into the beginning of steady-state operation (t=1400s) but on different scales: the second one uses log scale for easy comparison whereas the third one uses linear scale for better visualization of differences between drives. Click the buttons below each graph to switch the source data.

For more detailed description of the test and why performance consistency matters, read our original Intel SSD DC S3700 article.

  SanDisk Extreme Pro SanDisk Extreme II Intel SSD 730 Intel SSD 530 OCZ Vector 150
25% Spare Area

Similar to the Extreme II, the IO consistency is just awesome. SanDisk's firmware design is unique in the sense that instead of pushing high IOPS at the beginning, the performance drops close to 10K IOPS at first and then rises to over 50K and stays there for a period of time. The higher the capacity, the longer the high IOPS period: the 960GB Extreme Pro takes ~800 seconds before the IOPS drops to 10K (i.e. the drive reaches steady-state). I do not know why SanDisk's behavior is so different (maybe it has something to do with nCache?) but it definitely works well. Furthermore, SanDisk seems to be the only manufacturer that has really nailed IO consistency with a Marvell controller because Crucial/Micron and Plextor have had some difficulties and their performance is not even close to SanDisk.

However, I would not say that the Extreme Pro is unique. Both Intel SSD 730 and OCZ Vector 150 provide the same or even better performance at steady-state, and with added over-provisioning the difference is even more significant. That is not to say that the Extreme Pro is inconsistent, not at all, but for a pure 4KB random write workload there are drives that offer (slightly) better performance.

  SanDisk Extreme Pro SanDisk Extreme II Intel SSD 730 Intel SSD 530 OCZ Vector 150
25% Spare Area


  SanDisk Extreme Pro SanDisk Extreme II Intel SSD 730 Intel SSD 530 OCZ Vector 150
25% Spare Area


TRIM Validation

To test TRIM, I filled the drive with sequential data and proceeded with 60 minutes of 4KB random writes at queue depth of 32. I measured performance with HD Tach after issuing a single TRIM pass to the drive.

TRIM works for sure as the write speed is at steady 400MB/s.


Introduction, The Drives & The Test AnandTech Storage Bench 2013
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  • binarycrusader - Tuesday, June 17, 2014 - link

    Thanks, that explanation makes the comparison seems a lot more reasonable.

    By the way, NewEgg is selling the 480GB model for $379.99 today, which makes the Intel one slightly more appealing.
  • binarycrusader - Tuesday, June 17, 2014 - link

    There's still a DRAM cache though, so I'd like to see a torture test on SanDisk's drive before I could be confident. But I'm aware that's potentially bricking the drive so I can understand why you might not be able to do that.

    I agree that what SanDisk has done seems like it would help mitigate the need for a capacitor, but I just can't be confident about it until some tests are done.
  • brucek2 - Monday, June 16, 2014 - link

    Can anyone recommend a simple Windows utility for profiling your storage usage? I'm picturing something that runs in the background with an icon in the system tray I could mouseover to get a quick take on average daily data written, QD histogram, maybe read/write and/or size mix. It'd be great to be able to take a look at it when I'm reading articles like this to figure out which stats matter most to me.
  • matthew5025 - Tuesday, June 17, 2014 - link

    I recommend diskmon
  • Essence_of_War - Monday, June 16, 2014 - link

    Wherein SanDisk, not content with already having the top data rate and service time in the Destroyer benchmark, takes the title back from themselves.

    I'm very impressed with their commitment to product quality.
  • Antronman - Monday, June 16, 2014 - link

    At 200USD for 240GB, I'm just not sold.

    2x HyperX 3K 120GB in your choice of RAID configuration and you've got it, for 40-50USD cheaper.
  • jameskatt - Tuesday, June 17, 2014 - link

    Encryption is always going to slow down your drive. After all, it takes a lot of brute computation to do encryption.

    The biggest problem of hardware encryption is that you don't have the freedom to select your own encryption algorithm. For example, if the hardware encryption method is compromised then you are screwed if you rely on it.

    I would rather keep whole disk encryption at the OS level.
  • TheWrongChristian - Wednesday, June 18, 2014 - link

    Encryption in hardware is easy (at least easier than software) and probably adds very little in terms of latency and power budget. AES is just multiple rounds of XOR, ROM lookups and bit mixing. Quite easy to do in hardware quickly.

    AES-128 (the minimum AES level) is a long way from being considered broken.
  • SirKronan - Tuesday, June 17, 2014 - link

    Thanks for the review!! I am still going strong with my Extreme II and have yet to have any issues with it. Windows is still running fantastic, since the very first install on this drive. My dad's Extreme II is also running strong. I felt like I was taking a bit of a risk with an unknown when I got a somewhat less popular drive, but the current sale price back then was unbeatable, and to this day I have no regrets. Nice to see they are still coming to town and packing a punch!
  • uruturu - Tuesday, June 17, 2014 - link

    Why don't you test the drives in storage bench 2011-2013 with 25% OP???

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