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

  • US 7,383,292 B2
  • Filed: 07/14/2005
  • Issued: 06/03/2008
  • Est. Priority Date: 07/14/2005
  • Status: Active Grant
First Claim
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1. 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 by such file system, the file being defined to include data and metadata relating to the data but being in a ghosted form where the data has been moved to an alternate location to free space on the volume, the metadata of the ghosted file including ghosting information for being employed to at least partially retrieve the moved data for the file from the alternate location, the method in response to the file system receiving an open command from an application on the computing device with respect to the ghosted file and the file system upon receiving the open command noting that the ghosted file does not contain the moved data and returning an error, the method comprising a ghosting filter on the computing device:

  • intercepting such returned error and perceiving based thereon that the file is in fact in a ghosted form;

    commanding the file system to retrieve the ghosting information from the ghosted file and receiving such ghosting information;

    creating a handle corresponding to the ghosted file, and delivering the handle to the application as the response to the open command therefrom;

    receiving a read command from the application with respect to a portion of the data of the opened ghosted file, the read command having parameters including the handle and a definition of the portion including an offset into the portion of the data of the ghosted file and a read length with respect to such portion of the data;

    initiating reconstituting of the portion of the data of the ghosted file based on the received ghosting information and the data of the ghosted file at the alternate location; and

    after the portion of the data of the ghosted file has been reconstituted responding to the read command with the portion of the data requested.

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