A united cloud disk system, comprising: a principal service provider and a third party service provider, wherein the principal service provider comprises a united cloud disk server and storage resources; the united cloud disk server is configured to process a cloud disk service request transmitted by a united cloud disk client, an application, a third party engine or the third party service provider, and call the storage resources of the principal service provider and/or the third party service provider to provide united cloud disk services, wherein the united cloud disk services comprise at least one of: account services, directory services, folder services, container services, file services, object services, block services, sharing, online playing, offline download, upload/download by non-cloud disk users or searching; the storage resources are configured to be called by the united cloud disk server to access data; and the third party service provider comprises a united cloud disk third party service provider and a non-united cloud disk third party service provider and is configured to be called by the united cloud disk server, wherein the united cloud disk third party service provider refers to another service provider that includes united cloud disk servers and that provides the united cloud disk services, and the non-united cloud disk third party service provider refers to another service provider that doesn't include united cloud disk servers but provide the cloud disk services, cloud storage services or resources; wherein the united cloud disk server is further configured to back up data stored in a file, object or block by using any one of the following modes: mode 1, copying data stored by the principal service provider to storage resources provided by at least two other different third party service providers or copying the data to two other different physical locations of the principal service provider when there are no third party service providers so as to retain at least one piece of original data and two copies; mode 2, copying the data to storage resources provided by at least three different third party service providers or copying the data to the principal service provider when there are no third party service providers so as to retain at least one piece of original data and two copies; mode 3, copying the data stored by the principal service provider to storage resources provided by at least one other third party service provider or copying the data to another physical location of the principal service provider when there are no third party service providers so as to retain at least one piece of original data and one copy; mode 4, storing the data to storage resources provided by at least two different third party service providers or copying the data to the principal service provider when there are no third party service providers so as to retain at least one piece of original data and one copy. mode 1, copying data stored by the principal service provider to storage resources provided by at least two other different third party service providers or copying the data to two other different physical locations of the principal service provider when there are no third party service providers so as to retain at least one piece of original data and two copies; mode 2, copying the data to storage resources provided by at least three different third party service providers or copying the data to the principal service provider when there are no third party service providers so as to retain at least one piece of original data and two copies; mode 3, copying the data stored by the principal service provider to storage resources provided by at least one other third party service provider or copying the data to another physical location of the principal service provider when there are no third party service providers so as to retain at least one piece of original data and one copy; mode 4, storing the data to storage resources provided by at least two different third party service providers or copying the data to the principal service provider when there are no third party service providers so as to retain at least one piece of original data and one copy.