Study And Realization On Circle Quorum System Supporting Nonstop Network

Two big kinds of technologies, evading technology and fault-tolerant technology, are to enhance the reliability of computer network system. The avoiding technology mainly focuses on improving the reliability of component and parts of an apparatus, which cannot evade unplaned nework failures. When network failures happen, the fault-tolerant technology can guaranteed the network system still could reliably move through redundant Information.Quorum system, a special set system, belongs to the field of fault-tolerant technology. In this set system, the set element named quorum is a set of points, and every two quorums intersect. All quorums duplicate its data to the all points of other quorums, which increase data redundancy. Generally, this system has two kinds of fault-tolerant protocols, voting protocol and mutual exclusion protocol. The voting protocol can get valid data from quorum including failed points, while the mutual exclusion protocl can only get valid data from quorum without any failed points.The topology structure is the important character of quorum system. Topology structures reflect different organization forms of quorum, which has infection on performance, availability and so on. In real application, Different requirements on performance and availability of detail application characters has pushed research on quorum system with different topology structures.The foundation of quorum system is the ROWA protocol, which reads data from only one point and writes data to all points, proposed by Gifford in 1979, and the majority protocol, which reads data from N points and writes data to N+l points, proposed by Thomas in the same year. The latter has overcome the shortages such as load unbalance and the low reliability of reading data from the single point.In 1988, Mullender brought forward Byzantine quorum system with the voting protocol. In 1990, Cheung put forward grid quorum which imported reading quorum and writing quorum to divide reading and writing operations. This system reduced waiting time and increased system response capability. Peleg and Wool firstlyintroduced the mutual exclusion protocol into crumbling wall quorum system in 1995. In the same year, Change designed tree quorum system to release reading quorum size on the condition of higher root reliability, which the reading quorum level is higher, its size is smaller. Compared with tree quorum system, the diamond quorum system propose by Ada in 1999 increased reading quorum number to improving data parallel access. It also overcame the shortage that reading quorum size of tree quorum system had big changes on system response capability.All quorum systems with different topology structures had different quorum size, and they adopted which fault-tolerant protocols based on the single point reliability. The single point reliability is higher; the failure probability the small size quorum is smaller, while single point reliability is lower, the failure probability of half of points of the big size quorum is lower, which mutual exclusion protocol can improve high availability of quorum system.Along with development those years, quorum system has gained some academic results and primary application results such as distributed control and mobile communications. But, there are still some valuable researchable problems, one of which is all former quorum system are the quorum system based on reliable point connection, which suppose that the connection among points is reliable. However, in the real application the connection is always unreliable.This paper is research on quorum system based on unreliable point connection. Through analysis on cracking traditional quorum system, we designed a novel quorum system, circle quorum system, which its every two quorum clusters connect with each other in series like a circle. The quorum cluster including only three quorums is a small quorum system; every two quorum clusters intersected only one quorum. Circle quorum system used self-adaptive fault-tolerant protocol, which decided to...