If you plug the usb end of the data cable from the UPS into the USB port of your MC Mirror it will shutdown automatically when the UPS battery reserve reaches 10%. To test that you have a good connection between the UPS and the Mirror just pull the AC power cord from the UPS , this will cause it to start sending battery status messages to the WD Mirror which you will be able to see in the UI of the MIrror, and depending on whether you have notices setup you will start receiving emails about this event. There is no setup available for when it actually shutsdown the Mirror. I have created a suggestion at this link requesting that WD make UPS settings available to us. Please add your vote by following the link below;
http://community.wd.com/t5/Network-Product-Ideas/UPS-Settings-In-GUI/idi-p/821209
