My Cloud 100% CPU when USB Drive Attached

Hi syssecadmin, see if your issue is related to the following link.

http://community.wd.com/t5/WD-My-Cloud/Performance-on-a-WD-My-Cloud-or-WD-My-Cloud-EX4-degrades-and/m-p/662899/highlight/true#M5163

If your problem continues, I recommend you to contact support directly for assistance.

http://support.wd.com/contact/index.asp?lang=en