The Red Hat Enterprise Virtualization (RHEV) KVM management platform offers a cost-effective and stable alternative to building a virtual desktop infrastructure (VDI) solution. RHEV is originally based on a development by KVM specialist Qumranet. In 2008, Red Hat acquired the company and ported the software step by step from C# and .NET to Java. RHEV's current version 3.2 has been available since June 2012.

If you can manage without support from Red Hat, you can turn to the Red Hat-initiated open source oVirt project. This project is a starting point for Red Hat's RHEV product. However for business purposes, you will not want to use it in a production environment because of the lack of oVirt support as a VDI platform. Red Hat offers a 60-day trial subscription with support, installation instructions, and extensive documentation for testing the RHEV platform [1].

Architecture

A typical RHEV VDI environment (Figure 1) consists of the RHEV-M management server and one or more KVM-based RHEV-H hypervisor hosts. The RHEV Manager coordinates the RHEV-H server workloads; manages the VDI configuration, templates, and desktop pools; and takes care of automatically rolling out and deleting virtual machines. The RHEV Manager includes a JBoss application server with the RHEV engine and an SDK written in Python and Java. The available web applications include the administrator portal for administrators and the user portal for users, as well as a reporting engine. Since RHEV 3.2, RHEV and oVirt have offered a framework for the integration of third-party components directly in the RHEV Manager (Table 1).

Figure 1: Schematic representation of a RHEV environment.

RHEV-H servers provide the virtual machines. Each active VDI instance requires one. RHEV-H and RHEV-M server communication takes place via the libvirt stack and VDSM (Virtual Desktop and Server Manager) daemon.

Central storage is also necessary for virtual machines and templates. The following storage systems are supported: NFS, iSCSI, Fibre Channel, a local storage implementation using LVM, and other POSIX-compliant filesystems.

A thin client with SPICE (Simple Protocol for Independent Computing Environments) support or another terminal device (laptop, PC) will ideally be in place on the user side. The open source SPICE software and SPICE protocol of the same name act as the communication medium between desktop virtual machines (VMs) and the terminal device. User access to launch the connection to a virtual desktop always occurs through a web browser and the user portal. Depending on the thin client manufacturer, this process can also be hidden from the user. After successful authentication, one or more virtual desktops (and virtual servers) are available to VDI users on the user portal. A VM can be started by double-clicking the desired system.

SPICE

Open source SPICE is available free of charge. It allows a virtual desktop to be displayed over the network and ensures interaction between the VDI user and the virtualized desktop system. The guest system needs the SPICE agent to use SPICE. It communicates with the libspice library on the RHEV hypervisor. This library is in turn responsible for communication with the client.

The SPICE vdagent [2] is available as a package with many Linux distributions and supports SPICE operation on a Linux guest VM. For a Windows guest VM, the spice-guest-tools package [2] is used; it contains the additional drivers necessary for Windows.

SPICE has all the features that are important for users in daily operations. USB redirection makes it possible to pass on almost all USB devices from the thin client to the guest VM. Clipboard sharing allows users to copy between the guest VM and thin clients via the clipboard. Use of up to four screens with a guest VM is possible with multimonitor support.

Thanks to live migration, a VDI user can carry on working without interruption while their guest VM is migrated to a different hypervisor. Bi-directional audio and video transmission allows VoIP telephony, video conferencing, and movie playback in full HD. Transmission can be optionally encrypted through OpenSSL.

For rendering and hardware acceleration, SPICE uses OpenGL and GDI. Graphic computations are not performed by the client device CPU, but directly by the GPU. However, this requires corresponding support in the graphics chipset, which is almost always provided with modern devices.

SPICE usually creates very little network load; the protocol compares very well with other VDI protocols.

Templates and Pools

Templates and pools are essential components in a VDI setup with RHEV or oVirt. A template is the basis for a virtual machine in a VDI environment. Once a VM is configured with your desired system, software, and configurations, you can create a template from it.

A pool contains configuration for deploying virtual desktops for certain tasks or departments, such as, for example, offices at universities provided with desktops that have the necessary office software, but which users may change, or desktops used in exams, whose status is then reset after the event (stateless mode).