1. A computer-implemented method for restarting virtual machines, the computer-implemented method comprising: monitoring, by a computer, each server in a plurality of servers within a client virtual machine host environment via a network; responsive to the computer determining that a server failed in the plurality of servers within the client virtual machine host environment, retrieving, by the computer, a list of virtual machines that were executing in the failed server; determining, by the computer, a set of virtual machine dependency groups, in which all virtual machines of a dependency group must be started for an application to function properly, for virtual machines in the list of virtual machines based on properties corresponding to each respective virtual machine in the list of virtual machines; generating, by the computer, a restart plan that is parallelized and prioritized in which a virtual machine restart priority is a partial ordering of all the virtual machines, which are affected by the failed server in the client virtual machine host environment, into restart priority classes; restarting, by the computer executing the restart plan, the set of virtual machine dependency groups in parallel on a failover server of an alternate virtual machine host environment via the network; and restarting, by the computer further executing the restart plan, virtual machines within a particular restart priority class in parallel on a respective restart queue of the set of virtual machine dependency groups on the failover server of the alternate virtual machine host environment via the network.