Oracle VM is a platform that provides a fully equipped environment with all the latest benefits of virtualization technology. Oracle VM enables you to deploy operating systems and application software within a supported virtualization environment. Oracle VM insulates users and administrators from the underlying virtualization technology and allows daily operations to be conducted using goal-oriented GUI interfaces. The components of Oracle VM are shown in Figure 2.1, “Oracle VM Architecture”.
Oracle VM Manager: Used to manage Oracle VM Servers, virtual machines, and resources. It is comprised of a number of subcomponents, including an Application Development Framework (ADF) application, providing a familiar web-based graphical user interface (GUI); and a command line interface (CLI) allowing you to manage your infrastructure directly from the command line either via external scripts or by running manual command sequences.
Oracle VM Manager is an Oracle WebLogic Server application running on Oracle Linux. This can be a standalone computer, or part of a virtual machine running on an instance of Oracle VM Server.
While Oracle VM Manager is a critical component for configuration actions within the Oracle VM infrastructure, the virtualized environment can continue to function properly even if Oracle VM Manager experiences downtime. This includes the ability to maintain high availability and to perform live migration of virtual machines.
Oracle VM Server: A managed virtualization environment providing a lightweight, secure, server platform which runs virtual machines. At least one Oracle VM Server is required, but several are needed to take advantage of clustering.
Oracle VM Server is installed on a bare metal computer, and contains the Oracle VM Agent to manage communication with Oracle VM Manager. Dom0 is an abbreviation for domain zero, the management or control domain with privileged access to the hardware and device drivers. DomU is an unprivileged domain with no direct access to the hardware or device drivers. A user-domain (domU) is started and managed on an Oracle VM Server by dom0.
NoteSome of this terminology may vary depending on whether you are working with an x86 or SPARC based environment. Where possible, through this document, the alternate terminology is mentioned.
On x86-based systems, Oracle VM Server is based upon an updated version of the underlying Xen hypervisor technology, and includes Oracle VM Agent. It also includes a Linux kernel with support for a broad array of devices, file systems, and software RAID volume management. The Linux kernel is run as dom0 to manage one or more domU virtual machines, each of which could be Linux, Oracle Solaris, or Microsoft Windows™.
In contrast, Oracle VM Server for SPARC takes advantage of the hypervisor that is already included within the SPARC firmware, alongside the Oracle VM Agent for SPARC. The default Oracle Solaris operating system is usually promoted to act as the primary domain, which is equivalent to dom0 on x86 systems. Once the primary domain is in place, it can be used to create and manage further domains running different versions of the Oracle Solaris operating system.
Oracle VM makes use of Xen technology, when running on x86 servers, taking advantage of the Xen hypervisor. The Xen hypervisor is a small, lightweight bare metal hypervisor for x86-compatible computers. The Xen hypervisor securely executes multiple virtual machines on one host computer. Each virtual machine has its own guest operating system with almost native performance. The Xen hypervisor was originally created by researchers at Cambridge University, and derived from work done on the Linux kernel.
On SPARC systems, the SPARC hypervisor is built into the SPARC firmware and is generally referred to as the Logical Domains Manager (LDOM). As with the Xen hypervisor, each virtual machine is securely executed on a single computer and runs its own guest Oracle Solaris operating system. The SPARC hypervisor provides a broader range of virtualization features than the Xen hypervisor, due to the nature and design of SPARC hardware.
