Cloud data storage system

A cloud data storage system for multiple user_clients to access data of files over the cloud data storage system, comprising:

• at least one node, each node being connected to a corresponding first storage apparatus for respectively storing metadata of and related only to each data of file stored on a corresponding second storage apparatus, and being connected to the corresponding second storage apparatus for respectively storing data of files;
• at least two namenode modules, said namenode module having an active namenode module and at least one inactive namenode modules, the active namenode module being executed on one of said nodes for processing file operations issued by user_clients, the active namenode module issuing data access instruction for accessing and maintaining the metadata on the first storage apparatus;
• at least one datanode module, being executed on one of said nodes, each datanode module functions to scan and access a corresponding second storage apparatus connected to the node on which said datanode module is executed, said each node executing the datanode module storing only a partial metadata, the partial metadata is metadata corresponding to data of file stored on the second storage apparatus of node executing the datanode module;
• at least one namenode monitor module, being respectively executed on one of said nodes for monitoring health status of active namenode modules, and as the active namenode module malfunctions, the namenode monitor module wakes up inactive namenode module;
• wherein as the first storage apparatus connected to the node executing the active namenode module malfunctions and metadata is lost, one of the inactive namenode modules module will be woken up to execute cell recovery operation and retrieve the partial metadata from each node executing the datanode module for reconstructing an entire data which corresponds to all available data of files in currently active datanodes.