Research On Distributed Replica Location Model In ChinaGrid Data Management

The emerging grids need an efficient replica location model to solve the replica location problem.In the experience of developing the ChinaGrid Supporting Platform (CGSP), a grid middleware that addresses building a uniform platform supporting multiple grid-based applications, we found characteristics of locality in the process of replica location. One is that replica mappings are stored in the logical domains they belong to with high probability for security reasons. Another is that a query for replica mappings is initialized with high probability in the logical domain where the replica mappings are generated. Therefore, it has become the main challenge to build a replica location mechanism that can make use of these properties of locality to guarantee replica location performance and security. Some previous works have been done to build a replica location mechanism, but they are not suitable for replica location in a grid environment with multiple applications like ChinaGrid. In this paper, we present a distributed replica location model, Replica Service System (RSS). In the model, two kinds of replica mappings, Global Replica Mapping (GRM) and Local Replica Mapping (LRM) are defined based on domain properties. RSS can locate these replica mappings to reply to users'query about replica locations, and it has the merits of locality awareness, self-organization, and domain load balancing, Boundary-Chord is the key algorithm of RSS. It has the merits of statistically less message routing hops on both application-level and IP-level, and the manageability of data placement.In simulation experiments, RSS outperforms present distributed replica location model, P-RLS. Simulation results show that the algorithm has better performance than other structured DHT solutions to the replica location problem.