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[[modules-cluster]]
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=== Cluster-level shard allocation and routing settings
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_Shard allocation_ is the process of allocating shards to nodes. This can
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happen during initial recovery, replica allocation, rebalancing, or
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when nodes are added or removed.
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2015-06-22 17:49:45 -04:00
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One of the main roles of the master is to decide which shards to allocate to
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which nodes, and when to move shards between nodes in order to rebalance the
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cluster.
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There are a number of settings available to control the shard allocation process:
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2020-06-01 13:15:08 -04:00
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* <<cluster-shard-allocation-settings>> control allocation and
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rebalancing operations.
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* <<disk-based-shard-allocation>> explains how Elasticsearch takes available
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disk space into account, and the related settings.
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2020-06-01 13:15:08 -04:00
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* <<shard-allocation-awareness>> and <<forced-awareness>> control how shards
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can be distributed across different racks or availability zones.
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* <<cluster-shard-allocation-filtering>> allows certain nodes or groups of
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nodes excluded from allocation so that they can be decommissioned.
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2020-06-01 13:15:08 -04:00
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Besides these, there are a few other <<misc-cluster-settings,miscellaneous cluster-level settings>>.
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All of these settings are _dynamic_ and can be
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updated on a live cluster with the
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<<cluster-update-settings,cluster-update-settings>> API.
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include::cluster/shards_allocation.asciidoc[]
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2015-06-22 17:49:45 -04:00
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include::cluster/disk_allocator.asciidoc[]
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2015-06-22 17:49:45 -04:00
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include::cluster/allocation_awareness.asciidoc[]
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2014-09-26 15:04:42 -04:00
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2015-06-22 17:49:45 -04:00
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include::cluster/allocation_filtering.asciidoc[]
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2014-11-04 08:32:05 -05:00
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2015-06-22 17:49:45 -04:00
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include::cluster/misc.asciidoc[]
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