A data writing method based on a cloud storage system comprising at least: an access node, at least one management node, and at least one resource pool, wherein the at least one resource pool comprises at least one storage server, characterised in that the method comprises: receiving, by the access node, a data write request; sending the data write request to the management node, such that the at least one management node allocates a corresponding storage server for the data write request; when the at least one management node is at fault, identifying, by the access node, domain identification information contained in the data write request, and querying a pre-saved index according to the domain identification information, wherein the pre-saved index comprises a correspondence between the at least one resource pool and the domain identification information, wherein the pre-saved index is built by operations of: sending, by the access node, to each management node, a request for obtaining a correspondence between the at least one resource pool and domain identification information, and receiving the correspondence between the at least one resource pool and domain identification information sent by the management node; and saving the correspondence between the at least one resource pool and domain identification information in the pre-saved index; the method further comprises: identifying, by the access node, one of the at least one resource pool as a target resource pool that matches the domain identification information; determining, by the access node, one of the at least one storage server contained in the target resource pool as a target storage server, and writing data to be written into the target storage server. receiving, by the access node, a data write request; sending the data write request to the management node, such that the at least one management node allocates a corresponding storage server for the data write request; when the at least one management node is at fault, identifying, by the access node, domain identification information contained in the data write request, and querying a pre-saved index according to the domain identification information, wherein the pre-saved index comprises a correspondence between the at least one resource pool and the domain identification information, wherein the pre-saved index is built by operations of: sending, by the access node, to each management node, a request for obtaining a correspondence between the at least one resource pool and domain identification information, and receiving the correspondence between the at least one resource pool and domain identification information sent by the management node; and saving the correspondence between the at least one resource pool and domain identification information in the pre-saved index; sending, by the access node, to each management node, a request for obtaining a correspondence between the at least one resource pool and domain identification information, and receiving the correspondence between the at least one resource pool and domain identification information sent by the management node; and saving the correspondence between the at least one resource pool and domain identification information in the pre-saved index; the method further comprises: identifying, by the access node, one of the at least one resource pool as a target resource pool that matches the domain identification information; determining, by the access node, one of the at least one storage server contained in the target resource pool as a target storage server, and writing data to be written into the target storage server. identifying, by the access node, one of the at least one resource pool as a target resource pool that matches the domain identification information; determining, by the access node, one of the at least one storage server contained in the target resource pool as a target storage server, and writing data to be written into the target storage server.