.. _multinode_cluster_with_unified_nodes:


Multinode Cluster with Unified Nodes
------------------------------------

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


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

* Either four or six Unified nodes - each node combining Application and Database roles -
  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 and Unified nodes can be contained in separate firewalled networks.
* Database synchronization takes places between all Database roles, thereby offering Disaster Recovery 
  and High Availability.
* For 6 unified nodes, all nodes in the cluster are active. For an 8 node cluster (with latency 
  between data centers greater than 10ms) , the 2 nodes 
  in the DR node are passive, in other words, the **voss workers 0** command has been run
  on the DR nodes.
 
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

.. image:: /src/images/cluster-site.png

* the eight node cluster

.. image:: /src/images/6-node-topology.png

* 2 Web Proxy nodes in a DMZ

.. image:: /src/images/cluster-site-dmz67.png

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

.. image:: /src/images/cluster-site-dmz-admin-self-webprx.png