I have a Western Digital 2TB My Passport external drive connected via USB to my iMac. I partitioned the drive to include external backup, my TimeMachine backup, and by Carbon Copy Cloner bootable backups. Works perfectly. Occasionally when I shut down my iMac, the external drive light stays on steadily or blinks and the darkened screen gets caught in an endless spinning loop. What am I doing wrong? Do I need to eject the external drive every time before shutting down? If I need to do that, do I drag a drive icon to the trash, and if so, which one? Thanks.