architecture model

Author: jneczypor

modules/rosa-architecture.adoc

@@ -1,6 +1,29 @@
 // Module included in the following assemblies:
 //
 // * rosa_architecture/rosa_architecture_sub/rosa-architecture-models.adoc
+
+= ROSA with HCP architecture
+
+In ROSA with HCP, the ROSA service hosts a highly-available, single-tenant OpenShift control plane. The hosted control plane is deployed across 3 availability zones with at least 2 API server instances and three etcd instances. It is only accessible from the customer's VPC subnets. Customers access the hosted control plane through AWS PrivateLink. Customers can add an optional internet-facing API server endpoint to their ROSA with HCP cluster.
+
+The worker nodes are deployed in the customer's AWS account and run on the customer's VPC subnets. Customers can add one or more private subnets to the cluster VPC to ensure high availability. Worker nodes are shared by OpenShift components and applications. OpenShift components such as the ingress controller, image registry, and monitoring are deployed on the worker nodes hosted on the customer's VPC.
+
+= ROSA Classic architecture
+
+In ROSA Classic, both the control plane and the worker nodes are deployed on the customer's VPC private subnets.
+
+Customers can customize access patterns for their API server endpoint and Red Hat SRE management in the following ways:
+* Public, where API Server endpoint and Application Routes are all internet-facing.
+* Private, where API Server endpoint and Application Routes are private
+* Private with Private Link, where API Server endpoint and Application Routes are private, public subnets or NAT Gateways are not required in your VPC for egress, ROSA Service SRE Management uses AWS Private Link. 
+
+Note that although Public Subnets are needed in Private ROSA Classic clusters, no Control Plane or Worker nodes are deployed in public subnets. 
+
+In ROSA Classic, you can create either a zonal cluster, where Control Plane and Worker Nodes are hosted on a single AZ or regional cluster, where Control Plane is hosted on 3 AZs with an option to run Worker nodes on 1 or 3 AZs. 
+
+ROSA Classic clusters include Infrastructure Nodes in addition to Control Plane where OpenShift components such as Ingress Controller, Image Registry, and Monitoring are deployed. The Infrastructure Nodes and the OpenShift components deployed on them are managed by ROSA Service SRE. 
+
+
 [id="rosa-architecture_{context}"]
 = ROSA architecture on public and private networks
 

modules/rosa-hcp-classic-comparison.adoc

@@ -1,6 +1,5 @@
 // Module included in the following assemblies:
 //
-// * rosa_hcp/rosa-hcp-sts-creating-a-cluster-quickly.adoc
 // * rosa-architecture-models.adoc
 
 :_mod-docs-content-type: CONCEPT

rosa_architecture/rosa_architecture_sub/rosa-architecture-models.adoc

@@ -7,6 +7,7 @@ include::_attributes/attributes-openshift-dedicated.adoc[]
 toc::[]
 
 ROSA has the following custer topologies:
+
 * Hosted Control Plane (HCP) - The control plane is hosted in a Red Hat account and the worker nodes are deployed in the customer's AWS account.
 * Classic - The control plane and the worker nodes are deployed in the customer's AWS account.
 

rosa_hcp/rosa-hcp-sts-creating-a-cluster-quickly.adoc

@@ -26,10 +26,9 @@ Since it is not possible to upgrade or convert existing ROSA clusters to a {hcp}
 ====
 
 .Further reading
+* For a comparison between {hcp-title} and ROSA Classic, see the xref:../rosa_architecture/rosa_architecture_sub/modules/rosa-hcp-classic-comparison.adoc#rosa-hcp-classic-comparison_{context}[Comparing architecture models] documentation.
 * See the AWS documentation for information about link:https://docs.aws.amazon.com/rosa/latest/userguide/getting-started-hcp.html[Getting started with ROSA with HCP using the ROSA CLI in auto mode].
 
-include::modules/rosa-hcp-classic-comparison.adoc[leveloffset=+1]
-
 .Additional resources
 
 For a full list of the supported certificates, see the xref:../rosa_architecture/rosa_policy_service_definition/rosa-policy-process-security.adoc#rosa-policy-compliance_rosa-policy-process-security[Compliance] section of "Understanding process and security for Red Hat OpenShift Service on AWS".