The copy operation is copying files from D:/ to the USB stick.
When connecting the USB stick to the host and assigning a Shared Folder to it, copying the same files is even slower!
Not only it takes minutes(!) before the actual copy operation (about 300 files) begins, after copying has started, the VM hardly runs. I'm sitting here waiting for the VM to respond to my keyboard/mouse input... Almost same for my host OS. But the host OS still is more responsive.
Moreover, average copy speed is 12.1 KB/Sec.
Unbelievable...