.. _standard-deployment-topology:

Unified Node Deployment Topology
--------------------------------

.. _21.1|VOSS-837:


.. important::

   Choose between a unified node deployment or a modular architecture deployment.


In a Unified Node Deployment, VOSS Automate is deployed either as a single node cluster,
2 unified nodes, or a cluster of multiple nodes
with High Availability (HA) and Disaster Recovery (DR) qualities.   

Each node can be assigned one or more of the following functional roles:

* WebProxy - load balances incoming HTTP requests across unified nodes.
* Single node cluster - combines the Application and Database roles for use in a non-multi-clustered test environment.
* Unified - similar to the Single node cluster role Application and Database roles, but clustered with
  other nodes to provide HA and DR capabilities

The nginx web server is installed on the WebProxy, Single node cluster, and Unified node,
but is configured differently for each role.

In a clustered environment containing multiple Unified nodes,
a load balancing function is required to offer HA (High Availability providing failover between redundant roles).

VOSS Automate supports deployment of either the WebProxy node or a DNS load balancer. Here are some
considerations in choosing a WebProxy node vs. DNS:

* The Proxy takes load off the Unified node to deliver static content (HTML/JAVA scripts).
  When using DNS or a third-party load balancer, the Unified node has to process this information.
* DNS does not know the state of the Unified node.
* The WebProxy detects if a Unified node is down or corrupt.
  In this case, the WebProxy will select the next Unified node in a round robin scheme.

We recommend that you run no more than two Unified nodes and one WebProxy node on a physical server
(VMware server). Also recommended is that the disk subsystems be unique for each Unified node.

The following deployment topologies are defined:

* Test: a standalone, single node cluster with Application and Database roles combined. No
  High Availability/Disaster Recovery (HA/DR) is available.

  .. important::
  
     This deployment should be used for test purposes only.

* Production with Unified Nodes: in a clustered system, comprising:

  * 2, 3, 4 or 6 Unified nodes (each with combined Application and Database roles)
  * 0 to 4 (maximum 2 if 2 Unified nodes) WebProxy nodes offering load balancing.  The WebProxy nodes can be omitted if an external load balancer is available.