I am currently using Time Machine. I back up my iMac HD and my Lacie 250GB external drive to a Lacie 500GB drive using Time Machine. I'm a photographer and the 250GB drive is getting full. I purchased a Lacie 1TB external drive that I want to use for backup (Time Machine) and use the 250GB drive and the 500GB drive to store my images. What is the procedure to attempt this transfer?