Specifications

Red Hat Virtualization System

Architecture

A functional Red Hat Virtualization system is multi-layered and is driven by the privileged Red

Hat Virtualization component. Red Hat Virtualization can host multiple guest operating systems.

Each guest operating system runs in its own domain, Red Hat Virtualization schedules virtual

CPUs within the virtual machines to make the best use of the available physical CPUs. Each

guest operating systems handles its own applications. These guest operating systems schedule

each application accordingly.

You can deploy Red Hat Virtualization in one of two choices: full virtualization or

paravirtualization. Full virtualization provides total abstraction of the underlying physical

system and creates a new virtual system in which the guest operating systems can run. No

modifications are needed in the guest OS or application (the guest OS or application is not

aware of the virtualized environment and runs normally). Paravirualization requires user

modification of the guest operating systems that run on the virtual machines (these guest

operating systems are aware that they are running on a virtual machine) and provide

near-native performance. You can deploy both paravirtualization and full virtualization across

your virtualization infrastructure.

The first domain, known as domain0 (dom0), is automatically created when you boot the

system. Domain0 is the privileged guest and it possesses management capabilities which can

create new domains and manage their virtual devices. Domain0 handles the physical hardware,

such as network cards and hard disk controllers. Domain0 also handles administrative tasks

such as suspending, resuming, or migrating guest domains to other virtual machines.

The hypervisor (Red Hat's Virtual Machine Monitor) is a virtualization platform that allows

multiple operating systems to run on a single host simultaneously within a full virtualization

environment. A guest is an operating system (OS) that runs on a virtual machine in addition to

the host or main OS.

With Red Hat Virtualization, each guests memory comes from a slice of the host's physical

memory. For paravirtual guests, you can set both the initial memory and the maximum size of

the virtual machine. You can add (or remove) physical memory to the virtual machine at runtime

without exceeding the maximum size you specify. This process is called ballooning.

You can configure each guest with a number of virtual cpus (called vcpus). The Virtual Machine

Manager schedules the vcpus according to the workload on the physical CPUs.

You can grant a guest any number of virtual disks. The guest sees these as either hard disks

or (for full virtual guests) as CD-ROM drives. Each virtual disk is served to the guest from a

block device or from a regular file on the host. The device on the host contains the entire full

disk image for the guest, and usually includes partition tables, multiple partitions, and potentially

LVM physical volumes.

Virtual networking interfaces runs on the guest. Other interfaces can run on the guest like

Chapter 1.