There are times where cluster setup operations fail during the active clustered mailbox server installation.
Depending on where the failure occurred, when reviewing the resources in cluster administrator, it may appear that setup has fully completed. For example - there is an IP, Name, System Attendant, Information Store, and Database Instance resources. When a setup failure occurs, all or some of these resources are in a offline or failed state. Generally issuing an online command will bring the resources online leading people to believe that the installation was “successful”.
A clustered installation, regardless of resource state in the cluster, is never successful until the /newCMS or /recoverCMS command completes successfully. When creating your cluster, always allow the /newCMS command or /recoverCMS command to complete successfully – troubleshooting any failures that you have - so that you have a fully supported, fully installed clustered solution.