The Research On Key Technologies Of Replica Management For Data Grid

With the promotion of information technology, many business systems have been developed on the Internet in domains as diverse as government, business, and education. The combination of large dataset size, geographic distribution of user and resource, cooperative heterogeneous resource access and resource sharing on wide-area network results in stringent demands that are not satisfied by any traditional data management technology.Data Grid provides a mechanism for effective distributed resources sharing and transparent remote access to heterogeneous data on wide-area network. It can be applied to manage and share the large datasets effectively in domains such as government, business, and education.The Data Grid systems applied in domains mentioned above have the following characteristics: P2P topology, limited communication capability and limited storage capability. We call the computing environment with those characteristics "Low-end Computing Environment" and the Data Grid systems running on the Low-end Computing Environment "Low-end Data Grid". In distributed systems, data replication is a well-known and widely accepted technique to reduce data response time and network bandwidth consuming. However, the replication in Data Grid brings a series of replica management problems that affect the performance of Data Grid System greatly and replica management becomes a hot topic in Data Grid. The performance requirement of Low-end Data Grid is driving force for this thesis.The main contributions of the thesis in theoretical, technical and practical aspects are as follows:1. To give a uniform description of replication technology in Data Grid, the thesis presents a replication model NLPR on which replica management related mechanisms could be clearly described. A replica management service implementation skeleton-SCRMSA is proposed to provide a solution to open, transparent and flexible replica management services in different fields. Based on SCRMSA, the thesis puts forward a transparent, scalable and flexible data grid replica management system model DGRMSM.2. The thesis gives a new concept-Storage Alliance, based on which a dynamic replica creation strategy SADDRES is presented. SADDRES creates replicas by cache among Storage Alliances, and optimize the data distribution of a Storage Alliance according to users' access history.3. Replica location and selection mechanism is the key issue of datamanagement and access in Data Grid. To provide a load-balanced, high-performance, and high-scalable replica management, the thesis explores a hierarchical replica location and selection mechanism SAHRLSM. SAHRLSM includes SARRC replica catalog, SAHRLM replica location mechanism and SAHRSM replica selection mechanism. It also provides a series of methods to manage the dynamics of nodes, the dynamics of Storage Alliances and the consistency of SARRC replica catalog.4. It is a tough task to achieve the consistency of the replicas in deferent data grid applications. In the thesis, a replica consistency management service RCMS is introduced to provide distributed, high-efficient and flexible replica consistency management. Considering the characteristics of Low-end Data Grid, the thesis proposes a view and version based replica consistency management strategy VVRCOMS. VVRCOMS adopts version mechanism to manage the replicas and achieves high system performance by assuring the view consistency of users.5. In order to evaluate the mechanisms above, the Data Grid simulation tool-OptorSim is adopted. By extending OptorSim, we implement the replica management system StarRMS, which includes all mechanisms we proposed. The experimental results show that our replica management mechanisms are correct and effective. By adjusting environment variables of OptorSim, we test the performance of StarRMS in different computing environments. The results will be a valuable reference to the application of StarRMS in future.