Patent ID: 7284150

Claim:
A method for reliably storing data in a computer system, comprising: receiving a piece of data to be stored at a storage system: writing a first copy of the data to the storage system according to a first data redundancy scheme; writing a second copy of the data to the storage system according to a second data redundancy scheme; maintaining metadata of the data written to the storage system according to the second data redundancy scheme; copying the data written to the storage system according to the second data redundancy scheme to a backup storage system, wherein the copying is performed in response to a defined condition being met; and removing the data written to the storage system according to the second data redundancy scheme after it has been copied to the backup storage system, wherein the stored data includes both blocks of user data and attributes such as file names that are associated with collections of user data, and wherein the metadata is maintained by using a skeleton file system that replicates all the namespace and attribute information of the stored data and a set of delta files each of which records all the data updates that have been made to a corresponding file and that have not been copied to the backup storage system.