@mikael I want to virtualise just 1 windows server. There would be 2 psysical computers (called Master and Slave) with the virtualiser and there should be a synchronising mechanism to sync the guest windows machine from the Master physical computer to the Slave physical computer. The guest machine on Slave could be down all the time. In failover case (=Master system broken) the admin would start the replicated guest machine on Slave, so the users can continue their work with minimal downtime.
Now the question is what virtualisiation platform to use.