Merge pull request docker#944 from joaofnfernandes/improve-diagrams

Improve DDC diagrams

datacenter/dtr/2.1/guides/architecture.md

@@ -4,13 +4,29 @@ keywords: docker, registry, dtr, architecture
 title: DTR architecture
 ---
 
-Docker Trusted Registry (DTR) is a Dockerized application that runs on a Docker
-Universal Control Plane cluster.
+Docker Trusted Registry is a containerized application that runs on-premises
+or on the cloud and allows you to store and manage your Docker images. It
+needs to be deployed on a worker node managed by UCP.
 
-![](images/architecture-1.png)
+![](images/architecture-1.svg)
 
+Since DTR exposes the standard Docker API you can continue using the
+Docker CLI client to push and pull images to DTR.
+Universal Control Plane integrates out of the box with DTR so that you can
+deploy services and applications to your UCP cluster, using the Docker images
+you store in DTR.
 
-## Containers
+## Under the hood
+
+DTR needs to be deployed in a worker node managed by UCP.
+
+![](images/architecture-2.svg)
+
+For high-availability you can join multiple replicas to a DTR cluster.
+[Learn more about high availability](high-availability/index.md).
+
+
+## DTR internal components
 
 When you install DTR on a node, the following containers are started:
 
@@ -27,18 +43,8 @@ When you install DTR on a node, the following containers are started:
 
 All these components are for internal use of DTR. Don't use them in your applications.
 
-## Networks
-
-To allow containers to communicate, when installing DTR the following networks
-are created:
-
-| Name   | Type    | Description                                                                            |
-|:-------|:--------|:---------------------------------------------------------------------------------------|
-| dtr-br | bridge  | Allows DTR components on the same node to communicate with each other in a secure way  |
-| dtr-ol | overlay | Allows DTR components running on different nodes to communicate, to replicate DTR data |
-
 
-## Volumes
+## Volumes used by DTR
 
 DTR uses these named volumes for persisting data:
 
@@ -58,10 +64,23 @@ don't exist in the node, and creates them using the default volume driver.
 By default, the data for these volumes can be found at
 `/var/lib/docker/volumes/<volume-name>/_data`.
 
-## Image storage
+## Networks used by DTR
+
+To allow containers to communicate, when installing DTR the following networks
+are created:
+
+| Name   | Type    | Description                                                                            |
+|:-------|:--------|:---------------------------------------------------------------------------------------|
+| dtr-br | bridge  | Allows DTR components on the same node to communicate with each other in a secure way  |
+| dtr-ol | overlay | Allows DTR components running on different nodes to communicate, to replicate DTR data |
+
+
+## Where DTR stores images
 
 By default, Docker Trusted Registry stores images on the filesystem of the node
-where it is running.
+where it is running, but you can configure it to use an external storage system.
+
+![](images/architecture-3.svg)
 
 You can also configure DTR to use these storage backends:
 
@@ -74,11 +93,17 @@ You can also configure DTR to use these storage backends:
 For highly available installations, you should use a cloud storage system
 instead of an NFS mount, since they usually have better performance.
 
-## High-availability support
+## How you interact with DTR
+
+Since DTR exposes the standard Docker API you can continue using the
+Docker CLI client to push and pull images to DTR.
+
+Universal Control Plane integrates out of the box with DTR so that you can
+deploy services and applications to your UCP cluster, using the Docker images
+you store in DTR.
+
+![](images/architecture-4.svg)
 
-For load balancing and high-availability, you can install multiple replicas of
-DTR, and join them to create a cluster.
-[Learn more about high availability](high-availability/index.md).
 
 ## Where to go next