KVM vs LXC: What are the differences?

KVM (Kernel-based Virtual Machine) and LXC (Linux Containers) are two popular virtualization technologies used to create and manage isolated environments on a single physical host. Here are the key differences between KVM and LXC:

1. Virtualization Type: KVM is a hardware-level virtualization technology that uses a hypervisor to create and manage virtual machines (VMs) with their own operating systems and kernels. On the other hand, LXC is an OS-level virtualization method that utilizes Linux's containerization features to run multiple isolated user spaces on a shared kernel.

2. Isolation Level: KVM provides strong isolation between VMs as each VM runs with its own virtualized hardware components and operates as an independent system. LXC offers a lower level of isolation since containers share the host's kernel, potentially leading to less isolation between applications.

3. Resource Utilization: KVM consumes more resources as it emulates complete hardware components and requires separate kernels for each VM, resulting in higher resource overhead. LXC is more resource-efficient as containers share the host's kernel and utilize fewer resources, leading to faster startup times and efficient memory utilization.

4. Performance: KVM offers good performance and is suitable for running various operating systems and workloads. LXC provides superior performance for Linux-based applications since it avoids the overhead of emulating hardware components and running multiple kernels.

5. Portability: KVM provides higher portability due to its ability to run different operating systems and applications in isolated VMs. LXC containers are more suited for applications designed to run within Linux environments, limiting their portability to other operating systems.

6. Use Cases: KVM is suitable for scenarios requiring complete isolation, compatibility with various operating systems, and the need to run legacy applications. LXC is ideal for lightweight containerization of Linux applications, microservices, and cloud-native environments, emphasizing efficiency and rapid deployment.

7. Ecosystem and Tooling: KVM is supported by various management tools and platforms, including libvirt and tools integrated into popular virtualization platforms. LXC benefits from a rich ecosystem of container management tools like Docker, Kubernetes, and container orchestration frameworks.

8. Security: KVM offers better security through complete isolation between virtual machines. LXC's security relies on the shared kernel, potentially raising security concerns when hosting untrusted applications.

9. Overhead: KVM introduces higher overhead due to the need to emulate hardware components and run separate kernels for each VM. LXC has lower overhead since it shares the host's kernel and requires fewer resources for containerization.

In summary, KVM provides strong isolation and compatibility, making it suitable for diverse workloads, while LXC excels in efficiency and speed for Linux-based applications.