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Versioned file system with fast restore

  • US 8,799,231 B2
  • Filed: 08/30/2010
  • Issued: 08/05/2014
  • Est. Priority Date: 08/30/2010
  • Status: Active Grant
First Claim
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1. A non-transitory computer-readable medium having stored thereon instructions that, when executed by a processor, perform a method associated with a versioned file system comprising a set of versions, wherein each version comprises a tree of write-once objects rooted at a root directory manifest, and wherein versions may share objects, a method comprising:

  • associating a borrow window having a value to each of a set of versions in the versioned file system;

    in response to receipt from a user of a request to restore a file from a version X in the versioned file system to a current version Y, evaluating whether the file exists within a borrow window of the version X by determining a version created of all chunks of the file in version X, wherein, for each chunk i, the version created of chunk i is set to Vi;

    when the file exists within the borrow window of the version as evidenced by the borrow window value of current version Y minus the borrow window value of Vi being less than or equal to a borrow window value associated with Vi for each i, and in response to the request to restore, returning metadata associated with the file from the versioned file system so that the file has an appearance of being restored although contents of the file are not yet available to be provided to the user;

    when the file does not exist within the borrow window, performing a slow restore of the file; and

    upon receipt of a request to open the file that is distinct from the request to restore, returning contents of the file.

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