Deploying a Large Single Instance
This is the easiest to setup and configure. With this setup all of the Polling Engines will talk back to the Main Poller, and to the SQL Server. Web Console, Alerting, and Reporting will all be available from the same location, and you will only need to make changes in one location.
Deploying multiple Instances
I usually recommend this setup if the networks are separated, cannot talk back to each other, or if you have an IT Admin to manage for each Instance. Each Instance will need its own SQL Server to house all of the data. Web Console, Alerting, and Reporting is a little more difficult as you have to configure each one individually.
Combine multiple Instances with EOC
Enterprise Operations Console is specifically designed for incorporating multiple Instances into a single view that all locations can see the overall status of all devices. If you have to go the Multiple Instance route, EOC will take you to the Instance to see the Device information.
Adding a Poller
You will want to add a Poller if the Web Console states that you are near capacity, or if you want to poll multiple devices in a remote location. I have several customers that will use a Poller in one remote area to cover 4-5 locations to report back to the main server.
Thank-you for your response. We currently have three separate installations at our different co-location sites being managed with EOC. I think I would prefer to move to a single instance with additional polling engines to consolidate the licensing and resources. Thanks again!