1. A method of administering a plurality of virtual machines (‘VMs’) in a distributed computing environment, the distributed computing environment comprising a plurality of hosts, one or more of the hosts executing a virtual machine monitor (‘VMM’), each VMM supporting execution of one or more VMs, the method comprising: assigning, by a VMM manager, the VMMs of the distributed computing environment to a logical tree topology, including assigning one of the VMMs as a root VMM of the tree topology; and executing, by the VMMs of the tree topology, a reduce operation, including: sending, by the root VMM to each of other VMMs of the tree topology, a request for an instance of a particular VM; pausing, by each of the other VMMs, the requested instance of the particular VM; providing, by each of the other VMMs to the root VMM in response to the root VMM's request, the requested instance of the particular VM; and identifying, by the root VMM, differences among the requested instances of the particular VM including, performing a bitwise XOR operation amongst the instances of the particular VM.