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Selecting a directory of a dispersed storage network

  • US 9,658,911 B2
  • Filed: 02/14/2012
  • Issued: 05/23/2017
  • Est. Priority Date: 03/02/2011
  • Status: Expired due to Fees
First Claim
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1. A method for execution by a dispersed storage (DS) processing unit of a dispersed storage network (DSN) the method comprises:

  • obtaining a revision level of a global parent directory file of a global file structure, wherein the global parent directory file is represented by one or more data segments, in which respective data segments are error encoded to produce N number of encoded data slices for each data segment, and wherein the N number of encoded data slices for the respective data segments are dispersed separately in a distributed storage network, where only a read threshold number T of the particular N number of encoded data slices are needed to be retrieved from the distributed storage network to reconstruct each data segment to reconstruct the global parent directory file, where T is less than N, and wherein a local parent directory file also stores a local parent directory structure in encoded data slices in order for the local parent directory file and the global parent directory file to mirror each other, wherein the obtaining the revision level of the global parent directory file of the global file structure includes;

    transmitting a read request to the distributed storage network; and

    performing a slice-to-slice comparison of respective encoded data slices of the global parent directory file and the local parent directory file to identify a revision level indicator mismatch between respective encoded data slices of the global parent directory file and the local parent directory file;

    comparing the revision level of the global parent directory file with a revision level of a local parent directory file by comparing a revision level indicator included with at least one encoded data slice pertaining to the global parent directory file with a revision level of the local parent directory file;

    when the comparing of the revision level indicator included with the at least one encoded data slice pertaining to the global parent directory file with the revision level of the local parent directory file is unfavorable;

    retrieving encoded data slices pertaining to the global parent directory file from the distributed storage network;

    decoding the encoded data slices pertaining to the global parent directory file to reconstruct the global parent directory file;

    updating the local parent directory file based on the global parent directory file;

    accessing an entry of the global parent directory file that points to an address of a global child directory file, wherein the global child directory file includes an entry that points to an address of a data object;

    obtaining a revision level of the global child directory file, recovering and decoding encoded data slices pertaining to the global child directory file from the distributed storage network and using the global child directory file to update a local child directory file; and

    utilizing updated local parent and local child directory files to perform an access request regarding the data object.

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