File/Video serving - server cluster configuration

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http://serverfault.com – I currently have 5 servers. 1 server is used as the main server which holds all the video files, the other 4 are replicated and fetches videos from the main server using rsync. Videos are delivered through HTTP via nginx pseudo streaming. What I would want to ask is if there are better approach on this? Would it be better if 1 specific server only holds that file? eg: file1.mp4 will not be replicated across all the servers and would remain only on one server? Would this approach lessen the IO load? Because right now, viewers are randomly forwarded to any of those servers when viewing a video (HowTos)