Documents are replicated among servers comprising a search engine based on the value of each document by approximating its value as one of the top search results for one or more exemplary queries. Documents are allocated among servers comprising a search engine by calculating a relevance value for each document and then distributing the documents evenly to the servers. A subset of servers are selected from among a plurality of servers comprising a search engine using term-based, server-specific histograms reflecting the number of instances of the term in each document allocated to each server, and then selecting servers to service a query based on the documents on those servers.