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Support for host virtualization

The Host Utilities support virtualization, including products based on technologies such as Kernel-based Virtual Machine (KVM) and Xen. The products derived from KVM are Red Hat Enterprise Linux KVM, SUSE Linux Enterprise Server KVM, and RHEV. Products derived from Xen are Citrix XenServer, SUSE Linux Enterprise Server Xen, and Oracle VM.

Server virtualization is a method of dividing computer resources into multiple, isolated environments. In a virtual ecosystem, a host operating system runs one or more guest virtual machines in a simulated environment. Each guest virtual machine (VM) has access to all of the host's hardware. You can configure guest VMs in both full and paravirtualized modes.

Full virtualization includes a virtualization translation layer (VMM) that ensures that all guest system calls are translated to the native hypervisor's format. Using this approach, all guest operating systems run completely unmodified. Commercial products based on the full virtualization concept are RHEL-KVM, RHEV, and Oracle VirtualBox. KVM is a full virtualization solution for Linux on x86 hardware that contains virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module (kvm.ko) that provides the core virtualization infrastructure, and a processor-specific module (kvm-intel.ko or kvm-amd.ko). KVM is supported with Red Hat Enterprise Linux 5 Update 4 or later and Red Hat Enterprise Linux 6.0 or later.

Note: KVM leverages the Linux kernel's infrastructure and extends it to serve as a full-fledged hypervisor. Thus, any limitations that apply to the Linux kernel also apply to the KVM hypervisor.
Note: If you are using Oracle VM hypervisor, see the sections for configuring FC, iSCSI, and multipathing. In this guide, sections that refer to Red Hat Enterprise Linux also apply to Oracle Linux. Both operating systems use the same instructions for the tasks featured in this guide.

Paravirtualization support involves providing a paravirtualized network driver, a paravirtualized block I/O device (disk) driver, and a balloon driver to affect the operation of the guest virtual memory manager and provide CPU optimization for Linux guests. Both KVM and Oracle VM provide limited paravirtualization support for guest VMs. This approach to virtualization includes a slim hypervisor kernel running on the bare metal host hardware. Each guest OS must be ported to the hypervisor's kernel interface. The most renowned project utilizing the paravirtualization concept is Xen. Different commercial products based on Xen include OVM, Citrix XenServer, and SLES XEN.

Note: LUHU iSCSI best practices utilize the iSCSI software initiator from within the guest operating system. This applies to all the supported hypervisors.

Oracle VM is a server virtualization solution that consists of Oracle VM Server (OVS). This is a self-contained virtualization environment designed to provide a lightweight, secure, server-based platform for running virtual machines. OVS is based on an updated version of the underlying Xen hypervisor technology. Oracle VM Manager provides the user interface to manage OVS and guests.