Kenneth Miller from the Midwest ISO, and an InformationWeek Analytics contributor, said "The contained data centers that Microsoft championed addressed the compute portion of data center modularity but not the physical facility itself. Data centers [delivered in modular components] like Flex DC are more complicated on the design side due to local resources, building codes, support legacy equipment and specific customer requirements, but as long as the incremental building blocks are sized right, can remain standardized and meet an organization's technical requirements, this approach will meet many organization's needs."
HP's butterfly design contains a central building that contains the administrative offices, loading dock and space for storage and offices. The work is done in the quadrants which can be built in 400 or 800 KW units complete with heating and cooling. You supply the racks and computer equipment. The entire building is approximately 25,000 square feet with each quadrant between five to six thousand square feet each. HP is targeting power usage efficiency (PUE) rating which is calculated as a ratio of power for facilities divided by a the power used for computing (lower is better) of 1.25.
You can start with a core and one quadrant and add more quadrants as needed. Of course you achieve better cost savings per megawatt by building it all at once. The 50 percent cost savings cited by HP is based on a 3.2 MW butterfly. HP achieves the cost savings by leveraging its supply chain. By standardizing on the design and component selection, they reduce the number of parts and the labor to build each data center to spec. HP achieves economies of scale that they pass along to the customer. If you want custom features, that will, of course, change the price and the time to build.
Built on a slab, the heating and cooling is run over head through raised plenums. Cold air is vented to the cold aisle while hot air is extracted from the hot aisle. HP has four cooling designs: direct evaporative with direct expansion, indirect evaporative with direct expansion, Kyoto cooling, and air-to-air heat exchange with direct expansion. The cooling units are selected based on the local environmental conditions. To maximize floor space, the HVAC units are located outside the building with the plenums running through the outer wall. That keeps water, if evaporative systems are used, outside of the data center and away from electrical equipment.