Moving data from file on storage volume to alternate location to free space

• US 20070016621A1
• Filed: 07/14/2005
• Published: 01/18/2007
• Est. Priority Date: 07/14/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Suriyanarayanan, Guhan, Teodosiu, Dan, Robert, Christophe, Havewala, Sarosh, Balakrishnan, Shobana, Bjorner, Nikolaj
• Granted Patent: US 7,506,005 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/1737 for reducing power consumption or coping with limited storage space, e.g. in mobile devices saving storage space on storage devices G06F3/0608; power saving in storage systems G06F3/0625
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A computing device has a file stored on a storage volume by a file system and accessed through such file system. The file is defined to include data and metadata relating to the data, and at least a portion of the data of the file is removed from the file and stored at an alternate location such that the data does not occupy substantially any space on the volume and the file is in a reduced, ghosted form. The ghosted file is reconstituted for use by retrieving the data from the alternate location and associating such retrieved data with such ghosted file to form the reconstituted file.

Claims

1. A computing device having a storage volume, a file system managing the storage volume, and a file stored on the storage volume by the file system and accessed through such file system, the file being defined to include data and metadata relating to the data, at least a portion of the data of the file being removed from the file and stored at an alternate location such that the data does not occupy substantially any space on the volume and the file is in a reduced, ghosted form, the ghosted file being reconstituted for use by retrieving the data from the alternate location and associating such retrieved data with such ghosted file to form the reconstituted file.

2. The device of claim 1 wherein the computing device is a branch server and the alternate location is a hub server remote from the branch server, the hub server servicing a plurality of such branch servers.

3. The device of claim 1 wherein the ghosted file has been determined to be at least one of stale or irrelevant.

4. The device of claim 1 wherein the ghosted file on the volume is logically stored by the file system in a file location, and wherein ghosting the ghosted file does not alter the file location thereof, whereby a user can browse the volume by way of the file system to identify the ghosted file and the location thereof.

5. The device of claim 1 wherein the metadata of the ghosted file as resident on the volume includes substantially all the metadata from the file prior to ghosting, and also contains ghosting information for being employed to retrieve the data for the file from the alternate location.

6. The device of claim 1 wherein the file is defined to include data including primary data and secondary data, the primary data being larger than the secondary data, at least the primary data of the file being removed from the file and stored at the alternate location.

7. A method in connection with a computing device having a storage volume, a file system managing the storage volume, and a file stored on the storage volume by the file system and accessed through such file system, the file being defined to include data and metadata relating to the data, the method for freeing space on the volume as occupied by at least a portion of the file and comprising:

identifying the file;

identifying at least a portion of the data to be removed from the file;

moving the identified data from the file to the alternate location for being stored thereat such that the file is in a reduced, ghosted form;

marking space on the volume formerly occupied by the moved data as being free; and

amending the metadata of the now-ghosted file to include ghosting information including information that may be employed to retrieve the moved data for the file from the alternate location,

whereby the ghosted file may be reconstituted for use by retrieving the data from the alternate location and associating such retrieved data with such ghosted file to form the reconstituted file.

8. The method of claim 7 comprising moving the identified data from the file to the alternate location and storing such moved data at the alternate location along with an identification of the file.

9. The method of claim 7 wherein marking space formerly occupied by the moved data as being free results in a physical size of the ghosted file on the volume being reduced as noted in the metadata of the file and a logical file size of the ghosted file on the volume not being reduced as also noted in the metadata for the file.

10. The method of claim 7 further comprising amending the metadata of the now-ghosted file to set an attribute showing that such file is now ghosted, whereby an application on the computing device can determine from such attribute that the file is now ghosted, such application thus being made aware that such file must first be reconstituted into a non-ghosted form prior to accessing the data thereof.

11. The method of claim 7 comprising identifying the file based on having determined that the file is at least one of stale or irrelevant.

12. The method of claim 7 wherein the ghosted file on the volume is logically stored by the file system in a file location, and comprising not altering the file location of the ghosted file, whereby a user can browse the volume by way of the file system to identify the ghosted file and the location thereof.

13. The method of claim 7 wherein the file is defined to include data including primary data and secondary data, the primary data being larger than the secondary data, the method comprising:

identifying at least a portion of the primary data as the data to be removed from the file; and

moving the identified primary data from the file to the alternate location for being stored thereat such that the file is in a reduced, ghosted form.

14. The method of claim 7 further comprising reconstituting the ghosted file, such reconstituting comprising:

receiving a request to access the moved data of the ghosted file;

locating the ghosted file on the volume;

identifying the ghosting information in the metadata of the file;

locating the moved data of the file at the alternate location based on the identified ghosting information;

moving at least a portion of the located data from the alternate location to the computing device; and

associating the moved data with such ghosted file to form the reconstituted file.

15. The method of claim 14 further comprising amending the metadata of the reconstituted file to reset an attribute showing that such file is ghosted.

16. The method of claim 14 wherein associating the moved data with the ghosted file to form the reconstituted file comprises allocating space to be occupied by the moved data on the volume to the file and storing the moved data in the allocated space.

17. The method of claim 14 further comprising amending the metadata of the reconstituted file to remove the ghosting information.

18. The method of claim 14 comprising the file system receiving the request to access the moved data of the ghosted file and discovering that the ghosted file does not contain such moved data and returning an error, the computing device further having a ghosting filter, the ghosting filter intercepting the error employing the file system based on the intercepted error to obtain the ghosting information from the metadata of the ghosted file, and triggering reconstituting of the ghosted file based on the obtained ghosting information.

19. The method of claim 18 wherein the ghosting filter is a lower-level construct without access to the alternate location, the computing device further having a ghosting manager, the ghosting manager being a higher-level construct with access to the alternate location and interfaced with the ghosting filter, the ghosting filter triggering reconstituting of the ghosted file by requesting the ghosting manager to perform same.