Disclosed herein are embodiments for managing the placement of virtual machines in a virtual machine network. In an embodiment, a method involves determining whether to separate at least one virtual machine in a set of virtual machines supporting a process and running on a first host computer from other virtual machines in the set. If at least one virtual machine is to be separated, then at least one virtual machine is selected based on a number of memory pages changed. The selected virtual machine is then separated from the other virtual machines in the set.