Hierarchical quorum consensus: a new algorithm for managing replicated data

A novel algorithm for managing replicated data is presented. The proposed method is based on organizing the copies of an object into a logical, multilevel hierarchy, and extending the quorum consensus algorithm to such an environment. Several properties of the method are derived and optimality conditions are given for minimizing the quorum size. It is shown that, given a collection of n copies of an object, the method allows a quorum to be formed with n^0.63 copies versus [(n+1)/2] copies in the case of the majority voting algorithm. Tradeoffs between the proposed method and three other quorum-based methods are discussed, and the main features of each method are highlighted