A bit of an update since I still can't access mantis...
This morning I tried to be a bit tricky, and instead of accepting the default storage volume of my RAID array, I manually changed that to point at the system drive on the CORE when ripping a DVD. After that, when prompted to select a directory, I browsed through to the directory that is actually a symlink to my raid array. That is, I selected to rip to /home/public/data/videos/Main Storage Array  which is actually a symlink to /mnt/device/122/public/data/videos which is on my RAID array.
Doing this resulted in a failed rip, with a message about the disk being full. Now, the system drive has 84GB or so free, and the raid array is only 2% in use. So, I'm guessing the system is having trouble determining free space when looking at a symlink?
So, to recap, if I select to directly store things on my RAID array I get double entries for that media, one pointing at /mnt/device/122/public/data/videos and the other pointing at /home/public/data/videos/Main Storage Array 
Again, my guess is that UpdateMedia is traversing both trees.