File based volumes and file systems

• US 20070136548A1
• Filed: 12/13/2005
• Published: 06/14/2007
• Est. Priority Date: 12/13/2005
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Mane, Virendra
• Granted Patent: US 8,549,252 B2
• Time in Patent Office: Days
• US Class Current: 711/170
• CPC Class Codes: G06F 16/128 Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion use of snapshots for error detection or correction G06F11/14, G06F11/16

Abstract

A file-mapped volume is a logical volume in which the data storage of the logical volume is the data storage of a regular file associated with the logical volume. The regular file can be a file of a first file system, and a second file system can be built upon the file-mapped volume. These two file systems can have distinct inode address spaces, yet files of the first file system are easily moved to the second file system by changing pointers to inodes of these files. The second file system can be easily copied, attached, or transported by copying, attaching, or transporting the regular file containing the second file system, yet files in the second file system can be accessed in real time via file access routines of the operating system.

Claims

1. A computer-implemented method of operating data processing apparatus, said method comprising:

configuring a logical volume of computer data storage so that the logical volume is mapped to storage of an associated file of the computer data storage;

a file system manager of an operating system of the data processing apparatus creating and maintaining a file system on the logical volume; and

the file system manager accessing the associated file in response to a file access request from a user or application program for access to the file system.

2. The computer-implemented method as claimed in claim 1, which includes the file system manager producing a volume I/O request for access to the logical volume in response to the file access request from the user or application program, and the operating system converting the volume I/O request to a file I/O request to access the associated file and returning the file I/O request to the file system manager.

3. The computer-implemented method as claimed in claim 1, wherein the associated file is a file in a file system including user files, and the method includes the file system manager maintaining, in the file system on the logical volume, a respective file of system data for each of the user files.

4. The computer-implemented method as claimed in claim 3, wherein the system data are extended attributes of the user files, and the associated file is a hidden file.

5. The computer-implemented method as claimed in claim 1, wherein the file system is a snapshot copy of another file system, and the method includes transporting the snapshot copy by transporting a copy of the associated file.

6. The computer-implemented method as claimed in claim 1, wherein the file system manager has support for sparse files, and the associated file is a sparse file supported by the file system manager so that the file system manager allocates physical blocks to the logical volume as data are written to the logical volume.

7. The computer-implemented method as claimed in claim 1, which includes changing a logical-to-physical block mapping of the associated file so that physical blocks are de-linked from the logical volume in order to change the physical blocks of the logical volume.

8. Data processing apparatus comprising:

computer data storage; and

at least one data processor coupled to the computer data storage for access to data stored in the computer data storage;

wherein said at least one data processor is programmed with an operating system defining a file-mapped volume type in which a logical volume of the computer data storage is mapped to storage of an associated file of the computer data storage; and

wherein the operating system is programmed with a file system manager for maintaining file systems on logical volumes of the computer data storage, and the operating system is programmed for using the file system manager for maintaining a file system on a file-mapped volume.

9. The data processing apparatus as claimed in claim 8, wherein the operating system is programmed with a routine for associating a specified file with the file-mapped volume.

10. The data processing apparatus as claimed in claim 8, wherein the operating system is programmed for responding to a configuration command for creating and configuring the file-mapped logical volume so that the file-mapped logical volume becomes mapped to storage of the specified file.

11. The data processing apparatus as claimed in claim 8, wherein the operating system is programmed to respond to a request of the file system manager for access to a specified file-mapped volume by accessing storage of the associated file to which the specified file-mapped volume is mapped.

12. The data processing apparatus as claimed in claim 10, wherein the operating system accesses the storage of the associated file to which the specified file-mapped volume is mapped by sending a recursive call to the file system manager for reading or writing to the associated file to which the specified file-mapped volume is mapped.

13. The data processing apparatus as claimed in claim 8, wherein the operating system includes a volume layer for responding to volume I/O requests for access to the computer data storage of the logical volumes, a file system program layer including the file system manager for processing file access requests from users or applications, and a file-mapped volume interface layer between the file system layer and the volume layer, the file-mapped volume interface layer being programmed for receiving volume I/O requests from the file system layer for access to specified logical volumes, and

if a volume I/O request from the file system layer is a request for access to a specified file-mapped volume, converting the volume I/O request from the file system layer to a file I/O request to access data of the file associated with the specified file-mapped volume, and returning the file I/O request to the file system layer, and

if a volume I/O request from the file system layer is not a request for access to a specified file-mapped volume, passing the volume I/O request from the file system layer to the volume layer.

14. Data processing apparatus comprising:

computer data storage; and

at least one data processor coupled to the computer data storage for access to data stored in the computer data storage;

wherein said at least one data processor is programmed with an operating system including a file system manager for creating and maintaining file systems of directories and data files in the computer data storage; and

wherein the computer data storage contains a first one of the file systems, the first one of the file systems includes a data file in the computer data storage, and the operating system is programmed for using the file system manager for creating and maintaining a second one of the file systems in the computer data storage included in the data file.

15. The data processing apparatus as claimed in claim 14, wherein the operating system is programmed with a routine for specifying a file upon which another one of the file systems can be created and maintained by the file system manager.

16. The data processing apparatus as claimed in claim 15, wherein the routine responds to a configuration command by configuring a logical volume that is mapped to the computer data storage of the specified file.

17. The data processing apparatus as claimed in claim 14, wherein the operating system is programmed to respond to a request of the file system manager for access to a specified file-mapped volume by accessing the computer data storage of an associated file to which the specified file-mapped volume is mapped.

18. The data processing apparatus as claimed in claim 17, wherein the operating system accesses the computer data storage of the associated file to which the specified file-mapped volume is mapped by sending a recursive call to the file system manager for reading or writing to the associated file to which the specified file-mapped volume is mapped.

19. The data processing system as claimed in claim 14, wherein the operating system includes a volume layer for responding to volume I/O requests for access to the computer data storage, a file system program layer including the file system manager for processing file access requests from users or applications, and a file-mapped volume interface layer between the file system layer and the volume layer, the file-mapped volume interface layer being programmed for receiving volume I/O requests from the file system layer for access to specified logical volumes, and

if a volume I/O request from the file system layer is a request for access to a specified file-mapped volume, converting the volume I/O request from the file system layer to a file I/O request to access data of the file associated with the specified file-mapped volume, and returning the file I/O request to the file system layer, and

if a volume I/O request from the file system layer is not a request for access to a specified file-mapped volume, passing the volume I/O request from the file system layer to the volume layer.

20. The data processing apparatus as claimed in claim 14, wherein the first file system includes user files, and the second file system includes, for each user file, a respective file of system data with respect to said each user file.