1. A data center cooling system, comprising:a plurality of server racks aligned within a row in a human-occupiable workspace of a data center, the server racks supporting a plurality of heat-generating computing devices;
a warm air aisle positioned adjacent the server racks opposite the human-occupiable workspace and comprising a warm air inlet adjacent to a back side of the row of server racks and a warm air outlet in fluid communication with a warm air plenum;
a plurality of cooling modules each comprising at least one fan and at least one cooling coil mounted together in a housing, the cooling modules positioned to circulate a cooling airflow from the human-occupiable workspace, through the server racks, and to the warm air aisle; and
a single controller electrically and communicably coupled to each of the plurality of cooling modules in a serial arrangement and operable to perform operations comprising:
controlling the plurality of fans in the plurality of cooling modules to operate at a specified fan speed; and
controlling a plurality of valves fluidly coupled to the plurality of cooling coils in the plurality of cooling modules to modulate to a specified valve position,
wherein the serial arrangement of the single controller comprises the single controller being electrically coupled to each of the plurality of cooling modules by a direct current (DC) control power bus to receive power from a first cooling unit through the DC control power bus, independently of a loss of power to the remaining cooling units of the plurality of cooling units.