Hi,In this series of blog posts we will review the Resource State Machine from the Resource Host Server (RHS or Resource Monitor) point of view. Hopefully it will help you to design, develop and debug the Resource DLL you are developing to integrate your application with Windows Server 2008 & 2008 R2 Failover Clustering. IntroductionLet’s first review what components are involved in the process of managing of the resource state and how they interact with other components.If you need to integrate your application with Failover Clustering you have to write a Resource DLL. Basically this will allow your custom resource to interact with the cluster and perform common functional tasks, like bringing the resource offline or online. The Resource DLL is responsible for translating cluster resource state transition commands to commands specific for that application, and for bringing that application to a state corresponding to the current resource state. Read more: Clustering and High Availability, Part 2, Part 3