Patent ID: 7653612

Claim:
In a data processing system having a first data processor programmed with a first file system manager for managing access to a first file system, and a second data processor programmed with a second file system manager for managing access to a second file system, the first file system including a first file, the first file having data blocks in computer data storage, and the first file having data block mapping metadata mapping the data blocks of the first file to respective addresses in the computer data storage of the data blocks of the first file, a method comprising: a) the first file system manager managing access to the first file; and b) creating a second file in the second file system, the second file including a copy of the data block mapping metadata in the first file, the second file also including a link to the first file; and c) the second file system manager receiving a request from an application to read a specified data block from the second file, and responding to the request from the application by accessing the data block mapping metadata in the second file to obtain a respective address in the computer data storage for the specified data block in the first file, and the second file system manager formulating a storage access request for reading data from the respective address in the computer data storage of the specified data block in the first file, and the second file system manager sending the storage access request to the computer data storage, and d) the computer data storage responding to the storage access request by reading data from the respective address in the computer data storage of the specified data block in the first file, and e) returning to the application the data read from the respective address in the computer data storage of the specified data block in the first file.