A logical file system that distributes copies of files across various different physical storage resources yet provides a consistent view to the user of his or her data, regardless of which machine the user is accessing the files from, and even when the user’s computer is offline. The pump includes a piston installed in the bore in a reciprocating movable manner and defining an inlet path therein, an inlet valve to open or close an exit-side end of the inlet path according to a position of the piston, and an outlet valve provided at one side of the bore, operations of the inlet and outlet valves being contrary to each other. A can surrounds the cylinder and is loosely fixed relative to the housing. The distributed virtual infrastructure may comprise an enterprise private cloud infrastructure. The pendulum is tuned by adjusting the magnitude of a d. The consensus of the cooperators is based on a level of the first offer that each cooperator can achieve.