Method and system for consistent cluster operational data in a server cluster using a quorum of replicas
First Claim
1. A computer-implemented method, comprising:
- maintaining cluster operational data on a replica set comprising a plurality of replica members that are each independent of any node of a server cluster;
representing the cluster at a node if the number of replica members controlled by the node comprises at least a majority of the total number of replica members configured to operate in the cluster; and
determining which of the replica members of the replica set has operational data that is most updated, and replicating at least some of that operational data to the other replica members of the replica set.
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Abstract
A method and system for increasing server cluster availability by requiring at a minimum only one node and a quorum replica set of replica members to form and operate a cluster. Replica members, independent from the nodes, maintain cluster operational data. A cluster operates when one node possesses a majority of replica members, which ensures that any new or surviving cluster includes consistent cluster operational data via at least one replica member from the immediately prior cluster. Arbitration provides exclusive ownership by one node of the replica members, including at cluster formation, and when the owning node fails. Arbitration uses a fast mutual exclusion algorithm and a reservation mechanism to challenge for and defend the exclusive reservation of each member. A quorum replica set algorithm brings members online and offline with data consistency, including updating unreconciled replica members, and ensures consistent read and update operations.
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Citations
48 Claims
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1. A computer-implemented method, comprising:
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maintaining cluster operational data on a replica set comprising a plurality of replica members that are each independent of any node of a server cluster;
representing the cluster at a node if the number of replica members controlled by the node comprises at least a majority of the total number of replica members configured to operate in the cluster; and
determining which of the replica members of the replica set has operational data that is most updated, and replicating at least some of that operational data to the other replica members of the replica set. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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18. A system for providing consistent operational data of a previous server cluster to a new server cluster, comprising, a plurality of nodes, a plurality of replica members, each of the replica members maintaining an epoch number indicative of a state of the cluster operational data, at least one replica member having updated cluster operational data stored thereon by a first node including information indicative of a quorum requirement of a number of replica members needed to form a cluster, and a cluster service on a second node configured to 1) obtain control of a replica set of a number of replica members, 2) compare the number of replica members in the replica set with the quorum requirement, 3) form the new server cluster if the quorum requirement is met by the number of replica members in the replica set, and 4) determine which of the replica members of the replica set has data that is most updated.
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26. A computer-implemented method of operating a server cluster of at least three nodes, comprising:
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storing cluster operational data on a replica set of at least one replica member, each replica member being independent from any node;
at a first node, arbitrating with at least two other nodes for control of the replica set, the arbitration being performed for each replica member and comprising, attempting to obtain a right to exclusively reserve that replica member, and if the attempt is successful, exclusively reserving that replica member; and
representing the cluster at the first node if the replica set is controlled thereby and has consistent cluster operational data with respect to a previous cluster.
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37. A computer-readable medium having computer-executable instructions, comprising:
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representing a cluster by obtaining exclusive control of a majority of replica members in an available set thereof;
detecting a status change of one replica member with respect to the available set; and
taking action in response to the changed status to ensure that the replica members are consistent with respect to any update logged thereto.
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Specification