Link together Elastic documentation better

doc/administration/troubleshooting/elasticsearch.md

 # Troubleshooting Elasticsearch
 
+To install and configure Elasticsearch, and for common and known issues,
+visit the [administrator documentation](../../integration/elasticsearch.md).
+
 Troubleshooting Elasticsearch requires:
 
 - Knowledge of common terms.

doc/integration/elasticsearch.md

@@ -503,6 +503,8 @@ However, some larger installations may wish to tune the merge policy settings:
 
 ## Troubleshooting
 
+### Common issues
+
 Here are some common pitfalls and how to overcome them:
 
 - **How can I verify my GitLab instance is using Elasticsearch?**
@@ -631,6 +633,10 @@ Here are some common pitfalls and how to overcome them:
    You probably have not used either `http://` or `https://` as part of your value in the **"URL"** field of the Elasticseach Integration Menu. Please make sure you are using either `http://` or `https://` in this field as the [Elasticsearch client for Go](https://github.com/olivere/elastic) that we are using [needs the prefix for the URL to be accepted as valid](https://github.com/olivere/elastic/commit/a80af35aa41856dc2c986204e2b64eab81ccac3a).
    Once you have corrected the formatting of the URL, delete the index (via the [dedicated Rake task](#gitlab-elasticsearch-rake-tasks)) and [reindex the content of your instance](#adding-gitlabs-data-to-the-elasticsearch-index).
 
+### Low level troubleshooting
+
+There is more [low level troubleshooting documentation](../administration/troubleshooting/elasticsearch.md) for when you experience other issues, including poor performance.
+
 ### Known Issues
 
 - **[Elasticsearch `code_analyzer` doesn't account for all code cases](https://gitlab.com/gitlab-org/gitlab/issues/10693)**

doc/user/search/advanced_global_search.md

 # Advanced Global Search **(STARTER ONLY)**
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/109) in GitLab [Starter](https://about.gitlab.com/pricing/) 8.4.
-> - This is the user documentation. To install and configure Elasticsearch,
->   visit the [administrator documentation](../../integration/elasticsearch.md).
 
 NOTE: **Note**
-Advanced Global Search (powered by Elasticsearch) is not yet available on GitLab.com. We are working on adding it. [Follow this epic for the latest updates](https://gitlab.com/groups/gitlab-org/-/epics/153).
+Advanced Global Search (powered by Elasticsearch) is not yet available on GitLab.com. We are working on adding it.
+[Follow this epic for the latest updates](https://gitlab.com/groups/gitlab-org/-/epics/153).
 
 Leverage Elasticsearch for faster, more advanced code search across your entire
 GitLab instance.
 
+This is the user documentation. To install and configure Elasticsearch,
+visit the [administrator documentation](../../integration/elasticsearch.md).
+
 ## Overview
 
 The Advanced Global Search in GitLab is a powerful search service that saves

doc/user/search/advanced_search_syntax.md

@@ -3,14 +3,16 @@
 > **Notes:**
 >
 > - Introduced in [GitLab Enterprise Starter](https://about.gitlab.com/pricing/) 9.2
-> - This is the user documentation. To install and configure Elasticsearch,
->   visit the [administrator documentation](../../integration/elasticsearch.md).
 
 NOTE: **Note**
-Advanced Global Search (powered by Elasticsearch) is not yet available on GitLab.com. We are working on adding it. [Follow this epic for the latest updates](https://gitlab.com/groups/gitlab-org/-/epics/153).
+Advanced Global Search (powered by Elasticsearch) is not yet available on GitLab.com. We are working on adding it.
+[Follow this epic for the latest updates](https://gitlab.com/groups/gitlab-org/-/epics/153).
 
 Use advanced queries for more targeted search results.
 
+This is the user documentation. To install and configure Elasticsearch,
+visit the [administrator documentation](../../integration/elasticsearch.md).
+
 ## Overview
 
 The Advanced Syntax Search is a subset of the