1. A system comprising: plural virtualization systems configured in a cluster for operations of virtual machines; storage shared by the virtualization systems of the cluster, wherein the storage maintains encapsulated representations of virtual machine state of the virtual machines, wherein each of the encapsulated representations encodes at least one or more virtual disks for a particular virtual machine of the cluster; and a failover system that transitions at least one virtual machine affected by an interruption to another virtualization system of the cluster.