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Preventing pauses in algorithms requiring pre-image information concerning modifications during data replication

  • US 9,720,995 B1
  • Filed: 07/28/2015
  • Issued: 08/01/2017
  • Est. Priority Date: 01/09/2009
  • Status: Active Grant
First Claim
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1. A method performed by a distributed computing system comprising a plurality of computing nodes and a plurality of processes, the system including a first process holding a data region and executing on a first node, a second process on a second node, and a third process executing on a third node, the third process using the data region and holding a replica of the data region, the first, second, and third nodes being distinct from each other, the method being a method of replicating the data region from the first node to the second node, the method comprising:

  • determining to create a new replica of the entire data region in the second process on the second node directly from the first node, wherein, at a time of the determining, the second process does not hold any replica of the data region, wherein the second process includes an algorithm that, when executed, uses data of the data region stored on the first node and alters a datum of the data region, and wherein the datum as altered by the algorithm is transmitted to the first node for storage in the data region;

    initiating a capturing of an image of the entire data region on the first node and a replicating of the image on the second node;

    after initiating the capturing of the image, after capturing a first data item from the data region on the first node as a captured data item in the image, and before the replicating of the image on the second node is completed, (i) receiving a change to the first data item in the data region caused by the third process on the third node that changes the first data item to a changed data item in the data region on the first node, whereby the captured data item in the image and the changed data item in the data region on the first node are different, and (ii) sending, by the third process, the changed data item to the second node; and

    executing the algorithm on the second node, the algorithm using as an input the changed data item on the second node before the replicating of the image on the second node is completed.

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