[DOCS] Relocate `shard allocation` module content (#56535)

docs/plugins/discovery-ec2.asciidoc

@@ -236,7 +236,8 @@ The `discovery-ec2` plugin can automatically set the `aws_availability_zone`
 node attribute to the availability zone of each node. This node attribute
 allows you to ensure that each shard has copies allocated redundantly across
 multiple availability zones by using the
-{ref}/allocation-awareness.html[Allocation Awareness] feature.
+{ref}/modules-cluster.html#shard-allocation-awareness[Allocation Awareness]
+feature.
 
 In order to enable the automatic definition of the `aws_availability_zone`
 attribute, set `cloud.node.auto_attributes` to `true`. For example:
@@ -327,8 +328,9 @@ labelled as `Moderate` or `Low`.
 
 * It is a good idea to distribute your nodes across multiple
 http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-regions-availability-zones.html[availability
-zones] and use {ref}/allocation-awareness.html[shard allocation awareness] to
-ensure that each shard has copies in more than one availability zone.
+zones] and use {ref}/modules-cluster.html#shard-allocation-awareness[shard
+allocation awareness] to ensure that each shard has copies in more than one
+availability zone.
 
 * Do not span a cluster across regions. {es} expects that node-to-node
 connections within a cluster are reasonably reliable and offer high bandwidth

docs/reference/index-modules.asciidoc

@@ -105,7 +105,7 @@ specific index module:
     for the upper bound (e.g. `0-all`). Defaults to `false` (i.e. disabled).
     Note that the auto-expanded number of replicas only takes
     <<shard-allocation-filtering,allocation filtering>> rules into account, but ignores
-    any other allocation rules such as <<allocation-awareness,shard allocation awareness>>
+    any other allocation rules such as <<shard-allocation-awareness,shard allocation awareness>>
     and <<allocation-total-shards,total shards per node>>, and this can lead to the
     cluster health becoming `YELLOW` if the applicable rules prevent all the replicas
     from being allocated.
@@ -178,8 +178,8 @@ specific index module:
 `index.blocks.read_only_allow_delete`::
 
     Similar to `index.blocks.read_only` but also allows deleting the index to
-    free up resources. The <<disk-allocator,disk-based shard allocator>> may
-    add and remove this block automatically.
+    free up resources. The <<disk-based-shard-allocation,disk-based shard
+    allocator>> may add and remove this block automatically.
 
 `index.blocks.read`::
 

docs/reference/index-modules/allocation/filtering.asciidoc

@@ -3,8 +3,8 @@
 
 You can use shard allocation filters to control where {es} allocates shards of
 a particular index. These per-index filters are applied in conjunction with
-<<allocation-filtering, cluster-wide allocation filtering>> and
-<<allocation-awareness, allocation awareness>>.
+<<cluster-shard-allocation-filtering, cluster-wide allocation filtering>> and
+<<shard-allocation-awareness, allocation awareness>>.
 
 Shard allocation filters can be based on custom node attributes or the built-in
 `_name`, `_host_ip`, `_publish_ip`, `_ip`, `_host` and `_id` attributes.

docs/reference/modules.asciidoc

@@ -21,13 +21,7 @@ The modules in this section are:
 <<modules-discovery,Discovery and cluster formation>>::
 
     How nodes discover each other, elect a master and form a cluster.
-
-<<modules-cluster,Shard allocation and cluster-level routing>>::
-
-    Settings to control where, when, and how shards are allocated to nodes.
 --
 
 
-include::modules/discovery.asciidoc[]
-
-include::modules/cluster.asciidoc[]
+include::modules/discovery.asciidoc[]

docs/reference/modules/cluster.asciidoc

@@ -1,5 +1,9 @@
 [[modules-cluster]]
-== Shard allocation and cluster-level routing
+=== Cluster-level shard allocation and routing settings
+
+_Shard allocation_ is the process of allocating shards to nodes. This can
+happen during initial recovery, replica allocation, rebalancing, or
+when nodes are added or removed.
 
 One of the main roles of the master is to decide which shards to allocate to
 which nodes, and when to move shards between nodes in order to rebalance the
@@ -7,21 +11,21 @@ cluster.
 
 There are a number of settings available to control the shard allocation process:
 
-*   <<shards-allocation>> lists the settings to control the allocation and
+*   <<cluster-shard-allocation-settings>> control allocation and
     rebalancing operations.
 
-*   <<disk-allocator>> explains how Elasticsearch takes available disk space
-    into account, and the related settings.
+*   <<disk-based-shard-allocation>> explains how Elasticsearch takes available
+    disk space into account, and the related settings.
 
-*   <<allocation-awareness>> and <<forced-awareness>> control how shards can
-    be distributed across different racks or availability zones.
+*   <<shard-allocation-awareness>> and <<forced-awareness>> control how shards
+    can be distributed across different racks or availability zones.
 
-*   <<allocation-filtering>> allows certain nodes or groups of nodes excluded
-    from allocation so that they can be decommissioned.
+*   <<cluster-shard-allocation-filtering>> allows certain nodes or groups of
+    nodes excluded from allocation so that they can be decommissioned.
 
-Besides these, there are a few other <<misc-cluster,miscellaneous cluster-level settings>>.
+Besides these, there are a few other <<misc-cluster-settings,miscellaneous cluster-level settings>>.
 
-All of the settings in this section are _dynamic_ settings which can be
+All of these settings are _dynamic_ and can be
 updated on a live cluster with the
 <<cluster-update-settings,cluster-update-settings>> API.
 

docs/reference/modules/cluster/allocation_awareness.asciidoc

@@ -1,5 +1,5 @@
-[[allocation-awareness]]
-=== Shard allocation awareness
+[[shard-allocation-awareness]]
+==== Shard allocation awareness
 
 You can use custom node attributes as _awareness attributes_ to enable {es}
 to take your physical hardware configuration into account when allocating shards.
@@ -22,9 +22,8 @@ allocated in each location. If the number of nodes in each location is
 unbalanced and there are a lot of replicas, replica shards might be left
 unassigned.
 
-[float]
 [[enabling-awareness]]
-==== Enabling shard allocation awareness
+===== Enabling shard allocation awareness
 
 To enable shard allocation awareness:
 
@@ -76,9 +75,8 @@ allocates the lost shard copies to nodes in `rack_one`. To prevent multiple
 copies of a particular shard from being allocated in the same location, you can
 enable forced awareness.
 
-[float]
 [[forced-awareness]]
-==== Forced awareness
+===== Forced awareness
 
 By default, if one location fails, Elasticsearch assigns all of the missing
 replica shards to the remaining locations. While you might have sufficient

docs/reference/modules/cluster/allocation_filtering.asciidoc

@@ -1,10 +1,10 @@
-[[allocation-filtering]]
-=== Cluster-level shard allocation filtering
+[[cluster-shard-allocation-filtering]]
+==== Cluster-level shard allocation filtering
 
 You can use cluster-level shard allocation filters to control where {es}
 allocates shards from any index. These cluster wide filters are applied in
 conjunction with <<shard-allocation-filtering, per-index allocation filtering>>
-and <<allocation-awareness, allocation awareness>>.
+and <<shard-allocation-awareness, allocation awareness>>.
 
 Shard allocation filters can be based on custom node attributes or the built-in
 `_name`, `_host_ip`, `_publish_ip`, `_ip`, `_host` and `_id` attributes.
@@ -28,9 +28,8 @@ PUT _cluster/settings
 }
 --------------------------------------------------
 
-[float]
 [[cluster-routing-settings]]
-==== Cluster routing settings
+===== Cluster routing settings
 
 `cluster.routing.allocation.include.{attribute}`::
 

docs/reference/modules/cluster/disk_allocator.asciidoc

@@ -1,5 +1,5 @@
-[[disk-allocator]]
-=== Disk-based shard allocation
+[[disk-based-shard-allocation]]
+==== Disk-based shard allocation settings
 
 Elasticsearch considers the available disk space on a node before deciding
 whether to allocate new shards to that node or to actively relocate shards away

docs/reference/modules/cluster/misc.asciidoc

@@ -1,8 +1,8 @@
-[[misc-cluster]]
-=== Miscellaneous cluster settings
+[[misc-cluster-settings]]
+==== Miscellaneous cluster settings
 
 [[cluster-read-only]]
-==== Metadata
+===== Metadata
 
 An entire cluster may be set to read-only with the following _dynamic_ setting:
 
@@ -23,8 +23,7 @@ API can make the cluster read-write again.
 
 
 [[cluster-shard-limit]]
-
-==== Cluster Shard Limit
+===== Cluster shard limit
 
 There is a soft limit on the number of shards in a cluster, based on the number
 of nodes in the cluster. This is intended to prevent operations which may
@@ -66,7 +65,7 @@ This allows the creation of indices during cluster creation if dedicated master
 nodes are set up before data nodes.
 
 [[user-defined-data]]
-==== User Defined Cluster Metadata
+===== User-defined cluster metadata
 
 User-defined metadata can be stored and retrieved using the Cluster Settings API.
 This can be used to store arbitrary, infrequently-changing data about the cluster
@@ -92,7 +91,7 @@ metadata will be viewable by anyone with access to the
 {es} logs.
 
 [[cluster-max-tombstones]]
-==== Index Tombstones
+===== Index tombstones
 
 The cluster state maintains index tombstones to explicitly denote indices that
 have been deleted.  The number of tombstones maintained in the cluster state is
@@ -109,7 +108,7 @@ than 500 deletes. We think that is rare, thus the default. Tombstones don't take
 up much space, but we also think that a number like 50,000 is probably too big.
 
 [[cluster-logger]]
-==== Logger
+===== Logger
 
 The settings which control logging can be updated dynamically with the
 `logger.` prefix.  For instance, to increase the logging level of the
@@ -127,10 +126,10 @@ PUT /_cluster/settings
 
 
 [[persistent-tasks-allocation]]
-==== Persistent Tasks Allocations
+===== Persistent tasks allocation
 
 Plugins can create a kind of tasks called persistent tasks. Those tasks are
-usually long-live tasks and are stored in the cluster state, allowing the
+usually long-lived tasks and are stored in the cluster state, allowing the
 tasks to be revived after a full cluster restart.
 
 Every time a persistent task is created, the master node takes care of

docs/reference/modules/cluster/shards_allocation.asciidoc

@@ -1,15 +1,9 @@
-[[shards-allocation]]
-=== Cluster level shard allocation
-
-Shard allocation is the process of allocating shards to nodes. This can
-happen during initial recovery, replica allocation, rebalancing, or
-when nodes are added or removed.
-
-[float]
-=== Shard allocation settings
+[[cluster-shard-allocation-settings]]
+==== Cluster-level shard allocation settings
 
 The following _dynamic_ settings may be used to control shard allocation and recovery:
 
+[[cluster-routing-allocation-enable]]
 `cluster.routing.allocation.enable`::
 +
 --
@@ -58,8 +52,8 @@ one of the active allocation ids in the cluster state.
       Defaults to `false`, meaning that no check is performed by default. This
       setting only applies if multiple nodes are started on the same machine.
 
-[float]
-=== Shard rebalancing settings
+[[shards-rebalancing-settings]]
+==== Shard rebalancing settings
 
 The following _dynamic_ settings may be used to control the rebalancing of
 shards across the cluster:
@@ -94,11 +88,11 @@ Specify when shard rebalancing is allowed:
       allowed cluster wide. Defaults to `2`. Note that this setting
       only controls the number of concurrent shard relocations due
       to imbalances in the cluster. This setting does not limit shard
-      relocations due to <<allocation-filtering,allocation filtering>>
-      or <<forced-awareness,forced awareness>>.
+      relocations due to <<cluster-shard-allocation-filtering,allocation
+      filtering>> or <<forced-awareness,forced awareness>>.
 
-[float]
-=== Shard balancing heuristics
+[[shards-rebalancing-heuristics]]
+==== Shard balancing heuristics settings
 
 The following settings are used together to determine where to place each
 shard.  The cluster is balanced when no allowed rebalancing operation can bring the weight

docs/reference/monitoring/exporters.asciidoc

@@ -74,8 +74,7 @@ feature is triggered, it makes all indices (including monitoring indices)
 read-only until the issue is fixed and a user manually makes the index writeable
 again. While an active monitoring index is read-only, it will naturally fail to
 write (index) new data and will continuously log errors that indicate the write
-failure. For more information, see
-{ref}/disk-allocator.html[Disk-based Shard Allocation].
+failure. For more information, see <<disk-based-shard-allocation>>.
 
 [float]
 [[es-monitoring-default-exporter]]

docs/reference/redirects.asciidoc

@@ -502,4 +502,29 @@ See <<search-search>>.
 [role="exclude",id="modules-gateway-dangling-indices"]
 === Dangling indices
 
-See <<modules-gateway-dangling-indices>>.
+See <<modules-gateway-dangling-indices>>.
+
+[role="exclude",id="shards-allocation"]
+=== Cluster-level shard allocation
+
+See <<cluster-shard-allocation-settings>>.
+
+[role="exclude",id="disk-allocator"]
+=== Disk-based shard allocation
+
+See <<disk-based-shard-allocation>>.
+
+[role="exclude",id="allocation-awareness"]
+=== Shard allocation awareness
+
+See <<shard-allocation-awareness>>.
+
+[role="exclude",id="allocation-filtering"]
+=== Cluster-level shard allocation filtering
+
+See <<cluster-shard-allocation-filtering>>.
+
+[role="exclude",id="misc-cluster"]
+=== Miscellaneous cluster settings
+
+See <<misc-cluster-settings>>.

docs/reference/search/request/preference.asciidoc

@@ -3,7 +3,7 @@
 
 Controls a `preference` of the shard copies on which to execute the search.  By
 default, Elasticsearch selects from the available shard copies in an
-unspecified order, taking the <<allocation-awareness,allocation awareness>> and
+unspecified order, taking the <<shard-allocation-awareness,allocation awareness>> and
 <<search-adaptive-replica,adaptive replica selection>> configuration into
 account. However, it may sometimes be desirable to try and route certain
 searches to certain sets of shard copies.

docs/reference/setup.asciidoc

@@ -49,6 +49,8 @@ include::settings/audit-settings.asciidoc[]
 
 include::modules/indices/circuit_breaker.asciidoc[]
 
+include::modules/cluster.asciidoc[]
+
 include::settings/ccr-settings.asciidoc[]
 
 include::modules/indices/fielddata.asciidoc[]

docs/reference/upgrade/disable-shard-alloc.asciidoc

@@ -4,8 +4,8 @@ When you shut down a node, the allocation process waits for
 starting to replicate the shards on that node to other nodes in the cluster,
 which can involve a lot of I/O.  Since the node is shortly going to be
 restarted, this I/O is unnecessary. You can avoid racing the clock by 
-<<shards-allocation, disabling allocation>> of replicas before shutting down
-the node:
+<<cluster-routing-allocation-enable,disabling allocation>> of replicas before
+shutting down the node:
 
 [source,console]
 --------------------------------------------------