In the task manager of Windows 10, I see this:

Task manager

What does 100 % disk usage mean in Windows 10? How is the disk usage percentage calculated?

I am particularily confused by the first graph showing a constant percentage at 100 %, while the second graph shows read and write rates that vary.

  • 3
    It’s all about IOPS.
    – Daniel B
    Sep 7, 2016 at 7:32
  • have you watched the linked video in my answer? Does it answer everything you want to know? Sep 19, 2016 at 15:47
  • 1
    @magicandre1981 The part of the Channel 9 video you reference inspires at least as many questions as it answers. How are the values on the plot calculated from the values of the intervals [Complete Time,Disk Service Time-Complete Time] indicated in its title? Is the saturation of the controller implied by the values of this metric alone, or does Richards conclude this from other details of the test setup also? How is this related to what is shown in Task Manager?
    – rakslice
    May 9, 2018 at 9:12

1 Answer 1


The data come from the disk controller (Microsoft explained it in the video at 6m55 seconds). The disk controller tells Windows that the drive is busy and Windows displays it in the taskmanager graph. The Seagate drive is slow, replace it with a SSD.

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