18. A method for placing computing units in a data center, comprising:
placing a new computing unit in the data center at a candidate location, relative to one or more other previously-placed computing units, each computing unit having at least one communication element for communicating with at least one other computing unit using wireless communication, said at least one communication element forming a directionally-focused beam;
determining whether placement of the new computing unit at the candidate location creates permanent interference in the data center, wherein permanent interference exists when a first computing unit can communicate with a second computing unit, but the second computing unit cannot directly communicate with the first computing unit;
committing the new computing unit to the candidate location if there is no permanent interface; and
changing a location of at least one computing unit if there is permanent interference, followed by repeating said determining.