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Maintaining data consistency in mirrored cluster storage systems using bitmap write-intent logging

  • US 8,046,548 B1
  • Filed: 01/11/2008
  • Issued: 10/25/2011
  • Est. Priority Date: 01/30/2007
  • Status: Active Grant
First Claim
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1. A method for maintaining mirrored data consistency between a primary networked storage node and a secondary networked storage node using write-intent logging, the method comprising:

  • receiving an input/output (I/O) request at the primary networked storage node, wherein receiving the I/O request at the primary networked storage node comprises;

    checking a counter associated with an area of the disk targeted by the I/O request;

    checking the log entry associated with the area;

    placing the I/O request into a wait queue if the counter is zero and the log entry is not set;

    placing the I/O request into a hold queue if the counter is zero and the log entry is set; and

    processing the wait queue and the hold queue;

    logging the I/O request to a log at the primary networked storage node;

    storing the log to a disk associated with the primary networked storage node;

    executing the I/O request at the primary networked storage node;

    relaying the I/O request to the secondary networked storage node for execution;

    waiting for completion of both executing the I/O request at the primary networked storage node, and execution of the I/O request to the secondary networked storage node;

    clearing the log after waiting; and

    acknowledging completion of the I/O request after clearing the log.

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