1. A virtualized network storage system, comprising at least two network storage devices connected to a same Storage Area Network, SAN, wherein at least one of the network storage devices comprises a device management unit adapted to maintain a mapping relationship between global volume and local volumes of the network storage devices, and redirect an access to a global volume to a network storage device at which a global volume management unit of the global volume is located; at least one of the network storage devices comprises a global volume management unit adapted to execute an access to a global volume according to the mapping relationship between global volume and local volumes.