Patent ID: 7797275

Claim:
An object based storage system for maintaining cache coherence on a time basis in user file managers, the object based storage system comprising: a plurality of user file managers for obtaining, through a network, metadata and data from a metadata management server and an object-based storage device, the respective user file managers being associated with a processor and a memory for storing metadata and data, each of the individual user file mangers comprising: a writeback cache storing first metadata and first data, the metadata including structural information of the first data; a timer recording a time at which the first metadata and the first data are stored in the writeback cache; a metadata cache controller obtaining, through the network, new metadata from the metadata management server for replacing the first metadata when a current time at which the first data is requested is greater than the sum of the time recorded by the timer at which the first metadata is stored in the writeback cache and a predetermined time interval, and updating the writeback cache with the new metadata, such that the plurality of user file managers individually maintain cache coherency; and a data cache controller obtaining, through the network, new data from an object-based storage device for replacing the first data when a current time at which the first metadata is requested is greater than the sum of the time recorded by the timer at which the first data is stored in the writeback cache and a predetermined time interval, and updating the writeback cache with the new data, such that the plurality of user file managers individually maintain cache coherency.