Couldn't find a newer thread that addresses this. I have been doing time machine on my MBP on a 500G external HD. I upgraded my internal hard drive to 500G and moved my 256 to my optibay, and now time machine won't do any back ups. I want to get a refurbished time machine to do my backups, but I'm unsure how the time machine really works. Should I get a 2TB or will 1 TB suffice? Presumably I can just use my other 500G drive for normal storage, and the time capsule for backups so I shouldn't really need any spare space, but I'm concerned my time machine backups will fill the 1TB and I'll need to buy a new one (or replace the hard drive?) Thanks!