In this paper, we present a novel approach of virtual disk reconfiguration with performance guarantee in shared storage environment, which is important for storage maintenance tasks, especially for load balance. It identifies the surplus I/O resource of storage pools after satisfying performance requirement of virtual disks through EPYFQ scheduling algorithms, and gives high priority of using these I/O resources to data migration tasks. Moreover, our approach divides data migration task into multiple storage transactions, which can protect the consistency of the data in reconfigured virtual disks, such that the application I/O and migration I/O can execute concurrently. We also implement our approach into E-DM (Enhanced Device Mapper), a kernel module of Linux, and evaluate it. The result shows that the IOPS of virtual disks is decreased not more than 3% during reconfiguration.