OS X :: Storage Device Formatting And Transferring Info

I have a few questions about hard drive formatting and transferring. I currently have an imac i7 running snow leopard. I want to set up a workflow for archiving my personal files as well as client files. I do a lot of video work and I really like to save my stuff. I currently have a raw 1tb 7200rpm samsung running with a harddrive thermaltake reader. I would like to use the samsung 1 tb as an archiving disk. I have looked into drobo and those nice arrays, but I cannot afford it currently. What format should I format the 1tb? I want it as safe as can be. I plan to just store things. So I assume it will only need to be mac accessible, since I understand fat 32 only allows 4 gb transfers.

Should I format my storage drive to Mac os extended (journaled)? And that leads me to my second question. Natively I had already copied a bunch of my stuff to the 1tb harddrive when I first got it because my pc laptop was dying. So it is now a Fat format with stuff on it. I let the harddrive copy onto my desktop overnight in preparation of reformatting the drive. I hit get info on the folder on my desktop and compare to get info of the drive itself. There is about a 3 gb discrepancy between the folders. Where did the 3 gb go? And why? And HOW should I transfer files to make sure ALL of the documents are transferred?