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diff --git a/doc/features/server-quorum.md b/doc/features/server-quorum.md deleted file mode 100644 index 7b20084cea8..00000000000 --- a/doc/features/server-quorum.md +++ /dev/null @@ -1,44 +0,0 @@ -# Server Quorum - -Server quorum is a feature intended to reduce the occurrence of "split brain" -after a brick failure or network partition. Split brain happens when different -sets of servers are allowed to process different sets of writes, leaving data -in a state that can not be reconciled automatically. The key to avoiding split -brain is to ensure that there can be only one set of servers - a quorum - that -can continue handling writes. Server quorum does this by the brutal but -effective means of forcing down all brick daemons on cluster nodes that can no -longer reach enough of their peers to form a majority. Because there can only -be one majority, there can be only one set of bricks remaining, and thus split -brain can not occur. - -## Options - -Server quorum is controlled by two parameters: - - * **cluster.server-quorum-type** - - This value may be "server" to indicate that server quorum is enabled, or - "none" to mean it's disabled. - - * **cluster.server-quorum-ratio** - - This is the percentage of cluster nodes that must be up to maintain quorum. - More precisely, this percentage of nodes *plus one* must be up. - -Note that these are cluster-wide flags. All volumes served by the cluster will -be affected. Once these values are set, quorum actions - starting or stopping -brick daemons in response to node or network events - will be automatic. - -## Best Practices - -If a cluster with an even number of nodes is split exactly down the middle, -neither half can have quorum (which requires **more than** half of the total). -This is particularly important when N=2, in which case the loss of either node -leads to loss of quorum. Therefore, it is highly advisable to ensure that the -cluster size is three or greater. The "extra" node in this case need not have -any bricks or serve any data. It need only be present to preserve the notion -of a quorum majority less than the entire cluster membership, allowing the -cluster to survive the loss of a single node without losing quorum. - - - |