1. A method comprising: building a data overlay as a data structure on top of a logical space included in a distributed hash table (DHT) for a peer-to-peer system; wherein the logical space includes a plurality of DHT nodes having an associated plurality of DHT zones; building, in the data overlay, a topology of a tree having a plurality of levels each including one or more tree nodes associated with respective said DHT nodes, wherein: the first level of the tree includes a single tree node having a single tree node zone corresponding to the entire span of the logical space of the DHT and being logically divided into a plurality of said tree node zones respectively corresponding to: the tree nodes at each level of the tree; and parts of the logical space of the DHT; each said tree node includes a key member which identifies a key associated with its respective tree node zone. mapping a plurality of machines to the logical space of the DHT, wherein: each machine corresponds to one or more of more of the tree node zones; each machine selects as its representative node, from the one or more tree node zones corresponding thereto, the tree node corresponding to the largest size tree node zone; and each said representative node selects as its parent node another said representative node that is the representative node for an adjacent said tree node zone that has a larger size.