.. _multinode-modular-cluster-with-app-database-nodes:


Multinode Modular Cluster with Application and Database Nodes
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.. _21.1|VOSS-837:

.. index:: voss;voss workers
.. index:: web;web service


In order to achieve Geo-Redundancy using Application and Database nodes, you need the consider
the following:

* Six Application and Database nodes - 3 nodes with an application role and 3 nodes with a database role -
  are clustered and split over two geographically disparate locations.
* Two Web Proxy nodes to provide High Availability that ensure an Application role failure
  is gracefully handled. More may be added if Web Proxy nodes are required in a DMZ.

  It is strongly recommended *not* to allow customer end-users the same level
  of administrator access as the restricted groups of provider- and customer
  administrators. This is why Self-service web proxies as well
  as Administrator web proxies should be used.
  
  Systems with Self-service only web proxies are *only* recommended where the system
  is customer facing, but where the customer does not administer the system
  themselves.

* Web Proxy, application and database nodes can be contained in separate firewalled networks.
* Database synchronization takes places between all database role nodes, thereby offering Disaster Recovery 
  and High Availability.
* All nodes in the cluster are active.
 
Primary and fall-back Secondary Database servers can be configured manually. 
Refer to the Platform Guide for further details.

The diagrams in this section illustrate:

* the six node cluster
* 2 Web Proxy nodes in a DMZ
* 4 (2 admin, 2 Self-service) Web Proxy nodes in a DMZ


|6-node-modular-cluster|

|modular-cluster-site-dmz|

|modular-cluster-site-dmz-admin-self-webprx|


.. |6-node-modular-cluster| image:: /src/images/6-node-modular-cluster.png
.. |modular-cluster-site-dmz| image:: /src/images/modular-cluster-site-dmz.png
.. |modular-cluster-site-dmz-admin-self-webprx| image:: /src/images/modular-cluster-site-dmz-admin-self-webprx.png