Rackspace Hosting is getting into custom server design, and it is working with manufacturing partners with the Open Compute Project to get its tweaked versions of servers, storage arrays, and racks created by Facebook to run the social network manufactured by multiple suppliers. The hosting giant and cloud contender has made no …
I suspect part of the reason for the power difference is the rackspace design has power fitted to approx 1x208V 30A 3-phase circuit per zone. Since they use co-lo they may be billed based on the circuit size regardless of the amount of power draw, so it is beneficial to maximize circuit capacity.
Facebook might be using 480V 60A 3-phase which may be then split into 3x20A 277V to get ~4.4kW/zone (@ 80%) ?? sort of outside my realm of expertise.
If so - also likely then that Rackspace colos won't offer them 480V infrastructure to do something similar.