Cannot drag n drop

I have a 3tb external drive connected to a STi7. I had no issues adding the drive but when I want to load music and bring the drive up on my Mac, it says there is no room. i have to shut the ST down, pull the drive, connect it to my Mac to put the music on there and then connect it back to the ST and power it up. Please tell me there is an easier way

Edit: I decided to fire up my Linux computer and had no issues. It must be a OS-X thing