SanDisk X400 SSD Review (512GB)


Crystal Disk Benchmark is used to measure read and write performance through sampling of random data which is, for the most part, incompressible. Performance is virtually identical, regardless of data sample so we have included only that using random data samples.

SanDisk X400 512GB CDM

Crystal Disk Mark reveals very good numbers. It reached over 555MB/s read and over 536MB/s write. 4K reads and writes are very good as well, reaching over 42MB/s read and 151MB/s write. The higher QD32 results are very good as well.


The toughest benchmark available for solid state drives is AS SSD as it relies solely on incompressible data samples when testing performance. For the most part, AS SSD tests can be considered the ‘worst case scenario’ in obtaining data transfer speeds and many enthusiasts like AS SSD for their needs. Transfer speeds are displayed on the left with IOPS results on the right.

SanDisk X400 512GB AS SSD SanDisk X400 512GB AS SSD IOPS

In AS SSD the SanDisk X400 reached an overall score of 1102 points. Sequential speeds are a bit less than the other benches, reaching just 476MB/s read and 493MB/s write. 4K read and write is also much lower than crystal disk mark, reaching an 31MB/s read and 70MB/s write. Furthermore, it reaches nearly 95K IOPS read and 74K IOPS write, which is almost on par with its rating.

SanDisk X400 512GB AS SSD Copy

This AS SSD Copy Bench test is a true to life evaluation of performance as AS SSD creates three files (ISO/Program/Game), and simply moves them from one part of the SSD to another, recording their top speed and total transfer time. The best speed of 491MB/s was achieved via the ISO test which shows nearly performance saturation on the write side of the transfer, which is very nice to see.


Anvil’s Storage Utilities (ASU) are the most complete test bed available for the solid state drive today. The benchmark displays test results for, not only throughput but also, IOPS and Disk Access Times. Not only does it have a preset SSD benchmark, but also, it has included such things as endurance testing and threaded I/O read, write and mixed tests, all of which are very simple to understand and use in our benchmark testing.

SanDisk X400 512GB anvil

While providing us another look at performance, Anvil Storage Utilities shows overall, they are similar to that of our other tests. An overall score of 4770 was achieved, which is in line with other drives of this caliber. 4K speeds are much better than AS SSD’s results, but it seems sequential reads are lower yet again.


  1. blank

    Hey Sean-Is this a replacement for the Ultra 2??????
    Would have liked to have seen how large the SLC cache is-guessing around 8GB.

    If you ever get a chance-could you test a Samsung 650.It’s a strange one,it sits
    below the 750 EVO (which is not much more than a 640 EVO) and yet best I can
    tell it’s 3d nand.Perhaps lower binned nand that don’t make 850 spec…………….

    • blank

      No, it is not the Ultra II replacement. The Ultra II is part of their consumer product line. The X400 is part of their client/business product line.

      We will look into the Samsung 650.

  2. blank

    Hi Sean (or anyone:) ), I was about to buy a 512GB X400, but noticed that at, the older X300 series seems to have outperformed the X400 in write speeds by as much as 50%. Can anyone provide any insight?

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