I have an external USB powered HDD attached directly to a USB3 port on my 2012 mac mini. I never eject this drive as it is used daily and is where my media is stored. It seems that every time my mac goes to sleep and is woken up I get the above error message. It is really annoying because my mac is used purely as a plex server/player and is controlled almost exclusively with a remote control and I need to dig out the Bluetooth mouse to get rid of the error message. Anyone have any ideas how I can prevent this from happening?