The fail-over computer cluster enables multiple computing devices to operate using adaptive quorum rules to dictate which nodes are in the fail-over cluster at any given time. The adaptive quorum rules provide requirements for communications between nodes and connections with voting file systems. The adaptive quorum rules include particular recovery rules for unplanned changes in node configuration, such as due to a disruptive event. Such recovery quorum rules enable the fail-over cluster to continuing to operate with various changed configurations of its node members as a result of the disruptive event. In the changed configuration, access to voting file systems may not be required for a majority-group subset of nodes. If no majority-group subset remains, nodes may need direct or indirect access to voting file systems.