1. A method for generating an identifier for a new data object to be stored in a cluster of back-end servers of the kind where the cluster is organized into a plurality of nodes where each of the plurality of nodes in the cluster has a node identifier that is unique in the cluster, and where every back-end server in any of the plurality of nodes mirrors every other back-end server in the same node, the method comprising: selecting a path of a binary tree structure, in which the plurality of nodes are organized, based on a capacity of nodes along the path; identifying a first node as one at an end of the path in which the new data object is to be stored; generating a universal identifier for the new data object, the universal identifier having a node identifier part that uniquely identifies the first node in the cluster, a reserve part, and an object identifier part that uniquely identifies the object in the first node, the reserve part being at least in part generated as a pseudo-random value, wherein the node identifier part and the reserve part have a combined length that is a predetermined fixed length and the object identifier part does not uniquely identify the new data object on the cluster; and in the event of a node split creating at least two new nodes from the first node, setting one or more bits of the reserve part to identify a particular node of the new nodes, on which the new data object is stored following the split.