Evaluating Byzantine Quorum Systems

Replication is a mechanism extensively used to guarantee the availability and good performance of data storage services. Byzantine Quorum Systems (BQS) have been proposed as a solution to guarantee the consistency of that kind of services, even if some of the replicas fail arbitrarily. Many BQS have been proposed recently, but comparing their performance is not simple. In fact, it has been shown that theoretical metrics like the number of steps or communication rounds say as much about the practical performance of distributed algorithms as they hide. This paper presents a comparative evaluation of several BQS algorithms in the literature. The evaluation is based both on experiments and simulations. For that purpose, a framework for evaluating BQS called BQSNeko was developed. The results of the evaluation allow a better understanding of the algorithms and the tradeoffs involved.