Some examples described herein relate to a cluster computer system. In an example, a first node in a cluster computer system may determine that a second node has become unavailable. The first node may form a first sub-cluster with a plurality of nodes that are communicatively reachable in the cluster computer system. The first node may retain ownership over a first application running on the first node, to the exclusion of remaining nodes in the first sub-cluster, wherein retaining ownership over the first application comprises controlling access to a storage volume related to the first application. The first node may attempt to obtain ownership over a second application previously running on the second node before the second node became unavailable. In response to a successful attempt the first node may obtain ownership over the second application, to the exclusion of remaining nodes in the first sub-cluster.