Add warning for modifying services (#3966)

Author: rao-shwe

modules/manage/pages/manage-nodes/modify-services-and-rebalance.adoc

@@ -22,6 +22,18 @@ NOTE: You cannot add or remove the Data Service (kv) using this method.
 Adding or removing of the Data Service on an existing node is supported only through adding or removing nodes.
 For more information about adding or removing the Data Service on an existing node, see xref:manage:manage-nodes/manage-data-service-and-rebalance.adoc[Adding or Removing the Data Service on Existing Nodes].
 
+[WARNING]
+====
+When you modify (add or remove) services on existing nodes in a cluster, rebalance is triggered immediately to apply the changes.
+Removing a service instance reduces the cluster's capacity for that service.
+For certain services, such as the Index Service, removing the service may result in loss of replicas or entire indexes if no replicas exist,
+which can cause queries to fail.
+
+Removing all instances of a service deletes all data and metadata associated with that service, which means effectively removing the service from the cluster.
+For example, removing the last Index Service node deletes all indexes.
+For the Backup Service, physical backup repositories outside the cluster remain, but the Backup Service metadata about those repositories is deleted.
+====
+
 == Prerequisites
 
 Before modifying non-data services on nodes, make sure you have the following:
@@ -153,4 +165,4 @@ From the previous example, if `node3` was not running the index service, the fol
 ERROR: Node ns_1@node3 does not provide the index service
 ----
 
-For more information about the `couchbase-cli rebalance` command, see xref:cli:cbcli/couchbase-cli-rebalance.adoc[rebalance].
+For more information about the `couchbase-cli rebalance` command, see xref:cli:cbcli/couchbase-cli-rebalance.adoc[rebalance].

modules/rest-api/pages/rest-set-up-services-existing-nodes.adoc

@@ -26,6 +26,18 @@ Then trigger a rebalance operation.
 * For information about using the `POST /controller/rebalance` REST API to rebalance after node additions and removals, after a graceful failover and recovery, and after a hard failover, see xref:rest-api:rest-cluster-rebalance.adoc[Rebalancing the Cluster].
 ====
 
+[WARNING]
+====
+When you modify (add or remove) services on existing nodes in a cluster, rebalance is triggered immediately to apply the changes.
+Removing a service instance reduces the cluster's capacity for that service.
+For certain services, such as the Index Service, removing the service may result in loss of replicas or entire indexes if no replicas exist,
+which can cause queries to fail.
+
+Removing all instances of a service deletes all data and metadata associated with that service, which means effectively removing the service from the cluster.
+For example, removing the last Index Service node deletes all indexes.
+For the Backup Service, physical backup repositories outside the cluster remain, but the Backup Service metadata about those repositories is deleted.
+====
+
 === curl Syntax
 
 You must specify all known nodes in the cluster and the necessary cluster services topology.