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Building High Availavility

When running mission-critical services, you don’t want to depend on a single (virtual) machine to provide those services. Even when your systems would never crash or hang, from time to time you will need to do some maintenance and restart some services or even the whole machine. Fortunately, clusters were designed to overcome these problems and give the ability to reach a near 100% uptime for your services.
Introduction
There are a lot of different scenarios and types of clusters but here I will focus on a simple, 2 node, high availability cluster that is serving a website. The focus is on the availability and not on balancing the load over multiple nodes or improving performance. Of course this example can be expanded or customized to whatever your requirement would be.
To reach the service(s) offered by our simple cluster, we will create a virtual IP which represents the cluster nodes, regardless of how many there are. The client only needs to know our virtual IP and doesn’t have to bo…
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