ZZ: Cheap Practical BFT Using Virtualization

Despite numerous efforts to improve their performance and scalability, Byzantine Fault-Tolerance (BFT) techniques remain expensive, and few commercial systems use BFT today. This paper presents ZZ, a novel approach to construct general BFT services with a replication cost of practically f + 1, halving the 2f + 1 or higher cost incurred by state-of-the-art approaches. The key insight in ZZ is to use f + 1 execution replicas in the normal case and to activate additional replicas only upon failures.