6. The data center of claim 5, wherein the columnar structure includes plural layers of computing units.

7. The data center of claim 1, wherein at least a subset of computing units each includes at least one wired communication element for communicating with an external entity.

8. The data center of claim 1, wherein said at least three computing units are placed with respect to each other to avoid permanent interference, 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.

9. The data center of claim 1, wherein said at least three computing units form a switching fabric for transmitting payload data from a source computing unit to a destination computing unit via at least one intermediary computing unit.

10. The data center of claim 9, wherein at least one computing unit involved in transmission of the payload data is configured to use at least part of its memory resources, on demand and if available, as a buffer for temporarily storing the payload data being transmitted by the switching fabric.