KVM and LXC: Differences between types of Virtualization

Linux Containers and Kernel-Based Virtual Machine

Linux containers (LXC) such as KVM virtualization have certain advantages and disadvantages that influence the use cases in which these technologies are typically applied.

Linux containers

The current version of Linux Containers is primarily designed to support isolation of one or more applications, with plans to deploy full OS containers in the near future. You can create or destroy containers very easily and they are convenient to maintain.

System-wide changes are visible in every container. For example, if you update an application on the host machine, this change will apply to all sandboxes running instances of this application.

Since containers are lightweight, a large number of them can run simultaneously on a host machine. The theoretical maximum is 6,000 containers and 12,000 root file system directory link mounts. Additionally, containers are faster to create and have shorter startup times.

Portable, lightweight OS-based virtualization units that share the base operating system kernel, but at the same time act as sandboxes with their own file system, processes, and TCP /IP stack. They can be compared to Solaris Zones or Jails on FreeBSD. Since there is no virtualization overhead, they perform much better than virtual machines.

KVM virtualization

KVM virtualization allows you to boot entire operating systems of different types, even non-Linux systems. However, sometimes a complex setup is needed. Virtual machines are resource intensive, so you can only run a limited number of them on one server.

KVM represents the virtualization capabilities built into the Linux kernel itself.

Running standalone kernel instances generally means better separation and security. If one of the cores terminates unexpectedly, it does not shut down the entire system. On the other hand, this isolation makes it difficult for virtual machines to communicate with the rest of the system, so various interpretation mechanisms must be used.

The guest virtual machine is isolated from the main server changes, allowing it to run different versions of the same application on the host and the virtual machine. KVM also provides many useful functions, such as live migration. For more information on these capabilities, see the Red Hat Enterprise Linux 7 Virtualization Administration and Deployment Guide.

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