I don't understand disk usage in task manager.

[Haswellx86]

Sometimes when my SSD is reading/writing at almost its full speed the usage % is not even close to 100%, where as sometimes even doing a few MB/s or even KB/s can get the activity time to a 100% How exactly does the usage reading work?

[Guest]

Task manager isnt always accurate. Use hwinfo instead.

[Electronics Wizardy]

The type of IO really matters here. The max speed of a drive varies a lot depending on workload and if other factors like a empty cache have occured.