I have a Seagate drive that once i don't need to use it and i drag its icon to the trash, and it unmounts, the drive spins down. I then unplug the USB cable. I just bought a Western Digital My Passport 1TB drive. It does not spin down. I unmount it, and the icon disappears, but the drive just keeps on spinning away. Makes me nervous to unplug it, as I feel like its doing something. Is this normal or an issue?