A brokerage server for supporting a client, the brokerage server configured to be connected through the internet to the client and through the internet to at least one cloud storage, comprising: a server storage manager adapted to receive a cloud file access request for accessing the cloud storage from the client; a metadata manager to manage metadata including information about files stored in the cloud storage, this information including information indicating which cloud storage files are stored in, and a storage location of the file in that cloud storage, the metadata manager being configured to manage lists of files associated with each client and to provide these file lists to a client storage manager of the client via the server storage manager at regular time intervals or in response to a request from the client storage manager; a storage broker for supporting brokerage between at least one cloud storage and the client, the storage broker being adapted to select at least one cloud storage suitable for processing the cloud file access request from among a plurality of cloud storages (132, 134) in a cloud infrastructure connected through the internet using at least one of data attributes included in the file access request and the metadata; and an interface adaptor adapted to convert the file operation of the_file access request received from the client into a file operation suitable for an interface of the selected cloud storage and to convert the result of processing the file access request received from the selected cloud storage into a data format interpretable by the client, wherein the server storage manager is adapted to transfer the result of processing the file access request to the client. a server storage manager adapted to receive a cloud file access request for accessing the cloud storage from the client; a metadata manager to manage metadata including information about files stored in the cloud storage, this information including information indicating which cloud storage files are stored in, and a storage location of the file in that cloud storage, the metadata manager being configured to manage lists of files associated with each client and to provide these file lists to a client storage manager of the client via the server storage manager at regular time intervals or in response to a request from the client storage manager; a storage broker for supporting brokerage between at least one cloud storage and the client, the storage broker being adapted to select at least one cloud storage suitable for processing the cloud file access request from among a plurality of cloud storages (132, 134) in a cloud infrastructure connected through the internet using at least one of data attributes included in the file access request and the metadata; and an interface adaptor adapted to convert the file operation of the_file access request received from the client into a file operation suitable for an interface of the selected cloud storage and to convert the result of processing the file access request received from the selected cloud storage into a data format interpretable by the client, wherein the server storage manager is adapted to transfer the result of processing the file access request to the client.