Windows Server: Do I really need servers in remote locations?

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http://serverfault.com – I have one main site with several servers an a 2008/2012 environment. I have 4 remote sites that are physically close (a few miles apart) and are all connected to the main site by 20meg fiber on a private network. At each of the remote locations I have a windows server that users log in to and where their files and apps are located. There are many considerations to answering this question. But the first thing I am wondering is do I really need a server at each location? Users are just logging in to this server for permissions and a vast majority of my users are only using word, excel and ema (HowTos)