The following software upgrade strategies provide general guidelines and principles. Please use discretion at all times to develop your own software upgrade strategies that are sufficient for your application and environment.
Your original site started as a basic 4-server setup where the FrontEnds served as both the load balancer and application server. But, now your site has grown and now you need to have FrontEnds that are dedicated load balancers. This tutorial will walk you through the steps of how to migrate from the 4-server setup to a 6+ server setup.
This tutorial below assumes that you're going to use a server array to serve as the application level for your Deployment. Similarly, you can also have a Deployment with two application servers and a server array that's ready to scale-up when necessary. (see diagram). But, one of the advantages of having all application servers inside of a single server array is that you now have one place where you can manage and update all of your application servers. Be sure to configure your server array to have a minimum instance count of two at all times.
This tutorial assumes you have a running 4-server setup in production with Elastic IPs assigned to the FrontEnd servers.
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