I do this a lot, on machines which are annoyingly vendor-tweaked to allow a lot of dirty pages. Copying files to USB sticks happens instantly, but the unmount

I do this a lot, on machines which are annoyingly vendor-tweaked to allow a lot of dirty pages. Copying files to USB sticks happens instantly, but the unmount then takes an age - like, 20 minutes. This is a way to get a measure of the progress of the unmount. I generally have a sleep in there as well though ;)