Providing the latest version of a data item from an N-replica set
First Claim
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1. A method of managing replicas of a data item, the method comprising:
- responding to a request to update the data item by attempting to perform an update operation to replicas of the data item;
determining whether a first predetermined percentage of the members of a most-recently-established membership group were updated in the update operation, wherein the most-recently-established membership group includes those replicas that were updated in a most recent prior update to the data item; and
if the first predetermined percentage of the members of the most-recently-established membership group were updated in the update operation, then if all members of the most-recently-established membership group were not updated in the update operation, then establishing the replicas of the data item that were updated in the update operation as a new most-recently-established membership group.
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Abstract
Less-restrictive techniques are provided for ensuring that replicated-data systems will never provide out-of-date version of data items. A replicated-data system maintains (1) a version number, (3) a membership group identifier, and (6) a membership count, with each replica of a data item. These values are maintained in such a way as to allow the replicated-data system to reliably satisfy some read requests even though half, or less than half, of the replicas of the data item are available.
62 Citations
24 Claims
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1. A method of managing replicas of a data item, the method comprising:
responding to a request to update the data item by attempting to perform an update operation to replicas of the data item;
determining whether a first predetermined percentage of the members of a most-recently-established membership group were updated in the update operation, wherein the most-recently-established membership group includes those replicas that were updated in a most recent prior update to the data item; and
if the first predetermined percentage of the members of the most-recently-established membership group were updated in the update operation, then if all members of the most-recently-established membership group were not updated in the update operation, then establishing the replicas of the data item that were updated in the update operation as a new most-recently-established membership group. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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11. A method for handling a previously-offline replica of a data item, the method comprising:
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when the previously-offline replica comes online, populating a latest copy of the data item to the replica before the replica is established as a member of a most-recently-established membership group; and
in response to the addition of the previously-offline replica to the most-recently-established membership group, updating a membership count of all available members of the most-recently-established membership group. - View Dependent Claims (12, 23, 24)
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Specification