Research Of Replica Consistency Model In Data Grid

Data Grid provides a mechanism for effectively distributed resources sharing and transparent remote access to heterogeneous data on wide-area network.The replica is the key technique in the data grid. It is used to create the replica of remote data in the local region for avoiding the local host frequent visits to remote data. The importing of replica has many merits such as decreasing of data access delay, reducing the depletion of network bandwidth, balancing the load of server and improving usability of the data etc. But in the meantime, how to maintain consistency of various replicas of the same data within WAN and the usability of data access becomes one point and cruxes to solve in the current replica domain.This thesis aims to keep many replicas consistency of amount of mass data within data grid. The research is mainly reflected in these aspects:(1) Put forward amount of mass data of according to the model RCMTS(Replica Consistency Model based TimeStamp) to maintain the replica consistency of timestamp: the RCMTS model uses a timestamp technique to carry on the management to the replica, and uses the high autonomy characteristics of grid region, is divided into replica updating outside grid region and updating inside grid region two kinds of strategies, which improves the updating efficiency; according to the strategy of user view, the accuracy promised user to visit a LFN, the RCMTS provided to distribute for the data grid system, efficiently, vivid replica consistency management mechanism;(2) Put forward the method DSRL(A Dynamic Scalable Replica Location Method) of the dynamic and scalable replica location: the DSRL uses the index information node to support replica locaiton efficiently in the meantime to same replica with several data, and uses the local index node to support to the local replica location. Meanwhile, the thesis proposes a dynamic mapping technique , which according to the machine performance of the information index node it can well balanced allot the replica location information of the allotment, and supports an index information node with dynamic state to join and withdraw. The DSRL has a good extendibility, credibility and auto-adaptability, and can provide the highly effective replica location efficiency;(3) Use the grid simulation tool OptorSim to imitate the RCMTS model: analyzing the source code of OptorSim,and extending to it. We build up the environment of verification of the consistency model of the amount of mass data, and have got a group of experiment data which have reference value, accuracy and usefulness of RCMTS model verifying this thesis proposed, and providing a beneficial reference for its expansion and application.