Cluster Architecture

In a typical single server deployment Spectrum™ Spatial Analyst is comprised two nodes-
  1. Locate
  2. Connect

In order to achieve fail over the best approach is to have two or more servers each of which contains two nodes. That way each node is on a separate server, hence if that server fails the other one still has a node available. The installer will deploy both the nodes on each server that you install Spectrum™ Spatial Analyst on.

The following diagram illustrates this architecture showing two servers for Spectrum™ Spatial Analyst: