What is a VM (Virtual Machine)?
A Virtual Machine (VM) is a software-based computer that runs on a physical host (server) using a hypervisor. A VM boots and functions just like a real computer, but shares the physical hardware with other virtual machines.
In OT and industrial environments, VMs are often used to virtualise SCADA, Historian, Engineering Stations or MES systems and manage them more effectively.
🧠 How does a VM work?
- Hypervisor layer
- The hypervisor manages the hardware and ensures that several VMs can run alongside each other independently
- Examples: VMware ESXi, Microsoft Hyper-V, Proxmox, VirtualBox
- Guest operating system
- Each VM contains its own operating system (e.g. Windows Server, Linux)
- Fully isolated from other VMs on the same host
- Virtual hardware
- Virtual CPU, RAM, storage, network interface
- Can be tailored to the needs of the system
VMs can be copied, backed up, moved and restored like ordinary files.
🏭 Application in industrial environments
- Virtualising SCADA servers, Historian, MES and Batch Control
- Test and staging environments for PLC programming and HMI visualisation
- Domain Controllers or Active Directory in the OT segment
- Hosting Backup servers, patch management platforms, or Monitoring tools
Benefits:
- Efficient use of hardware
- Easier management and maintenance
- Faster Restore and migration
- Part of High Availability solutions
🔍 VM vs. physical server
| Aspect | VM | Physical server |
|---|---|---|
| Flexibility | Very high – quick to deploy or migrate | Limited – fixed hardware configuration |
| Recovery from failure | Quick via Snapshot or template | Slower recovery via physical replacement |
| Cost | Lower through consolidation | Higher when utilisation is low |
| Redundancy | Easy via High Availability and live migration | Complex and hardware-dependent |
Virtualisation is ideal for stable systems with predictable workloads.
🔐 Security aspects
- Each VM must have its own Firewall, Antivirus and patch management
- Apply RBAC and Access Control per VM
- Use Snapshots and Immutable Backup for recovery from ransomware
- Segment network traffic between VMs via VLAN or virtual switches
- Audit logins and activities via Audit logging
Virtualisation provides convenience, but it also increases the attack surface if it is not properly managed.
📌 In summary
A Virtual Machine is a flexible, scalable and efficient way to host industrial software in OT environments. It supports better availability, recovery and security — provided it is properly managed.