SYMPTOM:
One or more of the server(s) are unclustered after restarting a Strategy Intelligence Serverv 9.x cluster:

CAUSE:
One possible cause for this is that the some of the nodes were not configured to automatically join the cluster at start-up:

ACTION:
Configure all of the Strategy Intelligence Server 9.x nodes in a cluster to automatically join the cluster upon start-up. For detailed steps on how to accomplish this refer to the following Strategy Knowledge Base technical note:
KB12428: How to configure the MicroStrategy Intelligence Server to automatically join a cluster upon manual start-up