FTP to primary External HDD

I added a 1TB USB drive (fat32) to ATV and made it the primary drive. I then syncronized about 160 gb of iTunes files and my next step was to try to FTP files to the external drive. After about 10gb are transfered I get a “no more space” message from the FTP program. Is there something I can do to make sure the files are going to the USB drive and not the internal drive? I cannot imagine the 1TB USB drive being out of space.

Files placed in the Movies folder will be stored on the internal drive. Inside the Movies folder you will see a folder named ‘External Media’. Files placed here will be stored on the external drive.

it seems that all of my movies are being stored on the internal drive. i can’t find the external media folder. what gives?