Hybrid data center rack

A data center comprising:

• a data center facility;
• a plurality of information technology (IT) racks positioned in one or more rows in the data center facility, each IT rack including:
• an equipment enclosure including a front, a rear, and two or more partitions, each partition adapted to receive a piece of liquid-cooled information technology (IT) equipment, and
• at least one cooling door positioned on the rear of the equipment enclosure, the at least one cooling door having therein a heat exchanger, the heat exchanger being fluidly coupled to a liquid cooling system of at least one of one or more pieces of the liquid-cooled IT equipment,
• wherein the at least one cooling door is movable between:
• a first position where the cooling door extends across the rear of at least one partition so that air from an interior of the at least one partition flows through the cooling door, and
• a second position where air from outside the equipment enclosure flows through the cooling door;
• and
• wherein the IT rack further includes at least one additional equipment enclosure and a fan region positioned between at least one pair of equipment enclosures, the fan region adapted to receive one or more fan units to entrain air from the at least one pair of equipment enclosures and exhaust the air from a rear of the fan region.