| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程技術研究所 === 86 === Replica control has been an important issue for a distributed system.Replicated data objects not only provide high availability but also improve the performance of the system. One of the well-known replica control techniques is based on the employment of quorums, which are formed by grouping the replicated data objects in such a way that the consistency of the system can be ensured. Quorum-based replica control has been the subject of extensive research in the recent years. Most of the existing methods exploit some structures that are imposed upon the replicas in order to reduce the sizes of the quorums. However, they have some or all of the following disadvantages: 1. The load is not evenly distributed among the replicated data sites, and 2. The methods do not apply to an arbitrary number of sites. In this thesis, we propose a new replica control mechanism that is based on the concept of relaxed difference pair, which is an extension of the relaxed difference set. In particular, we present a simple and efficient a model for identifying relaxed difference pairs. This model eliminates the necessity of the time-consuming exhaustive search. It generates read-write coteries that are practically useful for an arbitrary number of sites in a distributed system. Unlike the previous methods, the model allows the flexibility of choosing appropriate read-write coteries that are most suitable for the target environment. Our mechanism is symmetric such that each site assume the same responsibility for the read/write operations. The sizes of the quorums are small in comparison with the existing methods.
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