The prevailing narrative in cloud-native circles often paints a picture of Kubernetes (K8s) inevitably replacing virtual machines (VMs). This is an oversimplification. The real story is far more interesting: K8s and VMs are not competitors; they are complementary partners building a robust, modern hybrid infrastructure.
Why VMs Are Still Irreplaceable
While K8s excels at orchestrating stateless, cloud-native applications, VMs remain the superior—or only—choice for several critical workloads:
1. Lifting-and-Shifting Legacy Systems: Monolithic, complex applications (think old ERP systems) that are difficult or impossible to containerize. Modernizing them often means running them reliably in a VM, not a container.
2. Specific Workloads: Applications that require unique kernel modules, specific OS configurations, or direct hardware access (e.g., via VFIO) often find a more stable home on a VM.
3. Strong Isolation: For scenarios with extreme security and compliance requirements, the hardware-level isolation provided by a VM is still considered the gold standard.
How They Coexist: The Patterns of Symbiosis
The synergy lies in choosing the right tool for the job, not forcing everything into a container.
1. Managing VMs Inside K8s: KubeVirt
This is the most elegant symbiosis. KubeVirt is a K8s extension that allows you to manage VMs using the familiar kubectl tool, right alongside your pods.
The Value: VM-based workloads can be scheduled and managed on the same unified platform as your containers, sharing networking and storage. This drastically reduces operational overhead.
2. Running K8s On Top of VMs
This is the most common path to production. Deploying your K8s nodes on VMs from vSphere, OpenStack, or any public cloud.
The Value: It leverages existing virtualization investments and expertise, providing a proven, secure foundation for your containerized applications.
The future of infrastructure is hybrid. The smart approach isn't to choose one over the other, but to use each where they excel:
- Use K8s for what it's best at: Stateless apps, microservices, and CI/CD pipelines.
- Use VMs for what they're best at: Legacy systems, specific workloads, and strong isolation needs.
With technologies like KubeVirt, we no longer have to choose. We can build a unified platform that embraces both containers and virtual machines, allowing each workload to run in its optimal environment.
Remember, technology should be a tool that serves you, not a dogma you serve.
