A Replication Strategy Based On Ant Colony Optimization In Storage Grid Environment

With the rapid increase of data amount, the need for reliability and expansibility of storage system has made a challenge to the storage grid, and the geographically distributed data-computing tasks are crying for the replication mechanism in the dummy storage. The replication mechanism can reduce the delay of data access and the consumption of bandwidth. We can increase the number of the data-accessing nodes by establishing many replica of a file in the WAN, and this will help to improve the load balance and enable the reliability of storage systems in a wide area.The issue that should be solved firstly in the replication mechanism is how to fix on the conditions and the strategies of the replication process. At present, there have been many researches on the replication strategies, and two of them are very popular. One is dynamic replication strategies, and the other is market based replication strategies. Although both of them have many advantages, there are still many shortages. For example, they can't provide different qualities of service (QoS) according to the users' requirements; and also don't take the physics factors of the grid system into account, like the read-write speed of the disk, congestion of the net and the accessing delay made by the bandwidth. So it has been an urgent issue that how to take the users' requirements and the physics factors of the grid system into account in order to improve the quality of the replication.This paper puts forward an improved replication strategy which is based on ant colony optimization (ACO), and we call it DRS -ACO. By using DRS -ACO, replication will proceed under three different QoS standards. The three different QoS standards are time optimization, price optimization and cost performance optimization. After finding the best replication path, the strategy will create a script file, and this file will create replicas along the path by using the transmitting function of the GridFTP. Then a nobody-guarded replication can be realized by the means of our strategy.