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Transaction commit is a problem much investigated, both in the databases and systems communities, from the theoretical and practical sides. We present a modular approach to solve this problem in the context of database replication on environments that are subject to Byzantine faults. Our protocol builds on a total order multicast abstraction and is proven to satisfy a set of safety and liveness properties. On the contrary of previous solutions in the literature, it assures strong consistency for transactions, tolerates Byzantine clients and does not need centralized control or multi-version databases. We present an evaluation of a prototype of the system.

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The reliability and availability of distributed services can be ensured using replication. We present an architecture and an algorithm for Byzantine fault-tolerant state machine replication. We explore the benefits of virtualization to reliably detect and tolerate faulty replicas, allowing the transformation of Byzantine faults into omission faults. Our approach reduces the total number of physical replicas from 3f +1 to 2f +1. It is based on the concept of twin virtual machines, which involves having two virtual machines in each physical host, each one acting as failure detector of the other.

No abstract