One of the fantastic things about using a virtualized environment for your key servers is that you get Disaster Recovery, Ransomware resilience and Backup in one solution
I have used Hyper-V as the virtualization platform but VMware, Virtualbox, KVM and others can also be used.
Replication involves maintaining a live copy of the virtual machines on a second physical server. The capability is built into Windows Server. The replica server is updated at intervals as short as 30s. In the event of a physical failure of one server, failover to the replica server is quick and easy.
You can also run backups of the virtual machines on the main server so that you can restore a machine to a particular (last good) point in time in the event that the files are corrupted – for example by Ransomware. Veeam and Altaro and others provide good products for this.
The easiest way to use Microsoft Hyper-V is to purchase 2 licenses for Windows Server 2019 standard and deploy this on two computers – the primary server and the replica server. The replica server can be lower spec hardware and is to be used temporarily if there is a physical fault in the primary server. This also gives the right to have two virtual installations of windows 2019 for say domain controller and main medical software server.
This is a relatively expensive solution – the two licenses together are over AUD 3000. If you have an existing domain controller there is a cheaper but much more difficult way to do it.
Microsoft Hyper-V server is a free product which runs on the bare metal and it is possible to configure replication on the platform.