Each virtual machine created on a host has its own QEMU instance.
libvirt also has APIs to interface with various block / storage and network configurations.įor QEMU/KVM virtual machines, libvirt talks with QEMU using QEMU-provided APIs. These software in turn interact with libvirt, which provides a hypervisor-neutral API to manage virtual machines. Users interact with virtual machines via one of the several available interfaces, like virt-manager, oVirt, OpenStack, or Boxes. Let's start with an overview of the virtualization stack, starting from the top-left of the graphic. Ending Stage 2 (Transitioning from Live to Offline State.The format followed for this article is: a textual representation of the slides, followed by a description of the content, roughly corresponding to what I would say during the presentation.
Libvirt qemu pdf#
The PDF version of slides are available here, but you won't need them to follow this post. This article is based on a presentation I recently delivered at the conference. The discussion will also cover known unknowns, i.e TODO items, for interested people to step up. It will discuss how live migration actually works, the constraints within which it all has to work, and how the design keeps needing new thought to cover the latest requirements. This discussion will go through the simple design from the early days of live migration in the QEMU/KVM hypervisor, how it has been tweaked and optimized to where it is now, and where we're going in the future. Live migrating virtual machines is an interesting ongoing topic for virtualization: guests keep getting bigger (more vCPUs, more RAM), and demands on the uptime for guests keep getting stricter (no long pauses between a VM migrating from one host to another).