Hi Fellows: I own a MacBook Air with 256 which I regret now that I realized that I need more storage anyways my question is the following. If I upgrade from Mountain Lion to Mavericks am I going to lose storage in the mac? I mean does the new software replaces the old OSX? I dont want to erase it all and then install I just want to upgrade so...to those who has experiences upgrading their machines am I going to lose if upgrade? Thanks Forum!