File System with Data Block Sharing

• US 20160063018A1
• Filed: 08/29/2014
• Published: 03/03/2016
• Est. Priority Date: 08/29/2014
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Das, Raj, Tipton, William, Verma, Surendra, Smith, Malcolm
• Granted Patent: US 9,727,575 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/122 using management policies backup systems G06F11/1446; file migration policies for HSM systems G06F16/185
• 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
• CPC Class Codes: G06F 16/13 File access structures, e.g. distributed indices arrangements of input from, or output to, record carriers G06F3/06
• CPC Class Codes: G06F 16/1752 based on file chunks

Abstract

To provide an operation that can quickly copy or rearrange a file, a file system allows stored data to be shared among two or more files or within a file. The file system provides an operation that allows an extent from one file to be copied into an extent of another file, or into a different extent in the same file if the extents do not overlap. To support such an operation, the file system tracks the storage locations for stored data for extents of a file, and whether the stored data for an extent of a file is shared with any other file or by another portion of the same file. When stored data is shared, writing to an extent of a file that refers to the shared stored data invokes a write operation to a new extent on the storage device, and the tracked information for the affected extents is updated.

Claims

1. A computer with a file system for managing storage of and access to a plurality of file system objects on one or more storage devices, comprising:

a storage medium storing data indicating whether stored data on the one or more storage devices are shared by file system objects;

a memory and a processor, with computer program code stored in the memory that, when executed by the processor, configures the processor to respond to requests from applications to access file system objects on the one or more storage devices, wherein writing data to an extent of a file for which stored data is shared writes data to a new extent in the one or more storage devices.

2. The computer of claim 1, wherein the data indicating whether stored data are shared comprises an index of shared extents.

3. The computer of claim 2, wherein the index includes, for a shared extent, a reference count indicating a number of file system objects sharing the extent.

4. The computer of claim 1, wherein the file system includes a command to copy a range of one or more extents from a source file to a range of extents in a destination file such that the source file and the destination file share the stored data for the range of blocks.

5. The computer of claim 4, wherein an application uses the file system command to make a copy of a file.

6. The computer of claim 4, wherein an application uses the file system command to rearrange a file.

7. The computer of claim 1, wherein a first file that shares stored data with a second file has an attribute set to cause writes to the first file to write data to a new extent on the one or more storage devices.

8. A computer-implemented process, comprising:

maintaining information tracking sharing of stored data by data files;

receiving a request to write data to a file;

determining whether the file shares stored data with other data files;

if the file shares stored data, then writing data for the file to a new extent in a storage device and updating the maintained information about sharing of the stored data.

9. The process of claim 8, wherein the data indicating whether stored data are shared comprises an index of shared extents.

10. The process of claim 9, wherein the index includes, for a shared extent, a reference count indicating a number of file system objects sharing the extent.

11. The process of claim 8, wherein the file system includes a command to copy a range of one or more extents from a source file to a range of extents in a destination file such that the source file and the destination file share the stored data for the range of extents.

12. The process of claim 11, wherein an application uses the file system command to make a copy of a file.

13. The process of claim 11, wherein an application uses the file system command to rearrange a file.

14. The process of claim 8, wherein a first file that shares stored data with a second file has an attribute set to cause writes to the first file to write data to a new extent in a storage device.

15. A computer-implemented process performed by a file system of a computer, comprising:

the file system receiving an indication of a source file from which data is to be copied, the data being stored in storage locations on a storage device;

the file system creating a destination file referencing the storage locations on the storage device for the data to be copied;

the file system storing data indicating that the data in the storage locations on the storage device are shared by source and destination files.

16. The computer-implemented process of claim 15, wherein the data indicating whether stored data are shared comprises an index of shared extents.

17. The computer-implemented process of claim 16, wherein the index includes, for a shared extent, a reference count indicating a number of file system objects sharing the extent.

18. The computer-implemented process of claim 15, wherein the destination file is a snapshot of the source file, the source file having a previous snapshot file, the process further comprising:

identifying the data to be copied as unmodified data from the previous snapshot file and modified data from the source file;

creating the destination file by referencing the storage locations on the storage device of the unmodified data from the previous snapshot file and of the modified data from the source file and updating the data indicating that the data in the storage locations on the storage device are shared by source and destination files and the previous snapshot file.

19. The computer-implemented process of claim 15, wherein the destination file receives rearranged data from the source file, the process further comprising:

identifying the data to be copied from the source file;

creating the destination file by ordering the identified data in the destination file and referencing the storage locations on the storage device of the identified data, and updating the data indicating that the data in the storage locations on the storage device are shared by source and destination files.

20. The computer-implemented process of claim 15, further comprising the file system confirming successful completion of copying of the data to the destination file.