Conclusion

Abstract

Quorum-based data replication is a well-established concept to improve operation availability on critical data objects in distributed systems whose components are (naturally) imperfect and subject to failures. Therefore, it is an important base concept to construct dependable distributed systems. In recent years, distributed systems have evolved from traditional statically deployed and fixed-sized systems to dynamic distributed systems. Their topology – in terms of the number of processes and their interconnecting communication infrastructure – cannot be immutably predetermined at design-time but instead is flexible and fluctuating with processes joining and deliberately departing from the system at run-time. The advent of such dynamic distributed systems demands for new means to cope with the emerging challenges posed by the dynamics. These challenges are a system’s ability to dynamically adapt to changing topologies – and possibly also to changing application requirements – and this adaptation to be performed in a best-possible manner with respect to the quality measure trade-off the system is specified for and supposed to implement.