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Using a sparse file as a clone of a file

  • US 8,521,690 B2
  • Filed: 04/18/2012
  • Issued: 08/27/2013
  • Est. Priority Date: 03/31/2009
  • Status: Expired due to Fees
First Claim
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1. A method for using a sparse file as a clone, the method comprising:

  • creating, by an application, a snapshot of a file, wherein the application is associated with a computer having a processor;

    requesting, by the application, the clone of the snapshot;

    generating, by the application, an empty sparse file, having at least one inode identifying the empty sparse file as the clone and pointing to the snapshot associated with the clone;

    whereby, the clone is created using the sparse file that begins as the empty sparse file; and

    reading data from the clone, wherein the reading from the clone comprises reading from the snapshot for unbacked data in the sparse file, whereby the snapshot presents the unbacked data to the clone and wherein reading from the snapshot for the unbacked data in the sparse file further comprises;

    responsive to a read of data at a logical offset location in the sparse file of the clone resulting in an indication that modified data exists at the logical offset location in the sparse file of the clone, scanning the at least one inode for the logical offset location in the snapshot where the data is located; and

    responsive to the scan of the at least one inode for the logical offset location verifying that the data at the logical offset location in the sparse file of the clone has been modified, preventing a read of the unbacked data from the snapshot.

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