  In distributed systems, data replication provides better availability, higher
read capacity, improved access efficiency and lower bandwidth requirements in
the system. In this paper, we propose a significantly efficient approach of the
data replication for serial isolation by using newly proposed Circular quorum
systems. This paper has three major contributions. First, we have proposed the
Circular quorum systems that generalize the various existing quorum systems,
such as Read-one-write-all (ROWA) quorum systems, Majority quorum systems, Grid
quorum systems, Diamond quorum systems, D-Space quorum systems,
Multi-dimensional-grid quorum systems and Generalized-grid quorum systems.
Second, Circular quorum systems not only generalizes but also improves the
performance over existing quorum systems of their category. Third, we proposed
a highly available Circular quorum consensus protocol for data replication
under serial isolation level that uses a suitable Circular quorum system for
read dominant scenario.
