I want to copy pictures and short videos off my camera and mobile phone to my mac mini, then after I've played around with them back them up to an external disk. What I'd really like to be able to do is then delete them from the mac mini to save space but not delete them from the back up itself. I just want to keep adding files to the backup as I go along. Ive got time machine running but as far as I can see if I delete the file from say my pictures it will then not be copied to the latest time machine backup, but may be available on previous ones. Iv'e also got iPhoto on the mac as well with all the pictures in there I want to keep, should I or can I just back that up instead?