P2P architecture is a viable option for enterprise backup. In contrast to dedicated backup servers, nowadays a standard solution, making backups directly on organization’s workstations should be cheaper (as existing hardware is used), more efficient (as there is no single bottleneck server) and more reliable (as the machines are geographically dispersed). The author present the architecture of a p2p backup system that uses pair wise replication contracts between a data owner and a replicator. In contrast to standard p2p storage systems using directly a DHT, the contracts allow their system to optimize replicas’ placement depending on a specific optimization strategy, and so to take advantage of the heterogeneity of the machines and the network.