1. A method for cloud application redundancy comprising: acquiring description information of a cloud application needing redundancy, wherein the description information comprises information about a backup network used at a redundancy site by the cloud application needing redundancy and information about a backup virtual machine used at the redundancy site by the cloud application needing redundancy, wherein the information about the backup virtual machine comprises an association between a virtual network adapter of the backup virtual machine and the backup network; creating the backup network according to the information about the backup network; creating the backup virtual machine according to the information about the backup virtual machine; and associating the backup virtual machine with the backup network according to the association between the virtual network adapter of the backup virtual machine and the backup network, wherein the information about the backup virtual machine used at the redundancy site by the cloud application needing redundancy further comprises an identifier, specifications of the backup virtual machine, and information about a second storage unit occupied at the redundancy site by the backup virtual machine, wherein creating the backup network according to the information about the backup network comprises sending a virtualized network creating command to a virtualization module at the redundancy site, and wherein the virtualized network creating command carries the information about the backup network so that the virtualization module at the redundancy site: determines, according to the virtualized network creating command, a virtual switch used by the cloud application needing redundancy; and configures the information about the backup network for a port group of the virtual switch.