US Patent 7685179 Network flow for constrained replica placement

A deterministic technique is used for assigning locations to object replicas in a data center, while taking the various constraints into account that guarantee high availability and fast recovery. Example constraints include not putting the replicas on the same machine and not on the same rack, in case the rack or the network switch goes down. Also, because power distribution units (PDUs) can fail, the two replicas are not put on the same PDU. A solution is guaranteed to be found, if one exists.