Chapter 1. An Overview of Red Hat Enterprise Virtualization

This introductory chapter will help you understand the following things before deploying and managing Red Hat Enterprise Virtualization (RHEV):

Virtualization and its basic concepts
An overview of Kernel-based Virtual Machine (KVM) RHEV
The RHEV architecture and its components
Hardware and software prerequisites

The virtualization overview

Hardware virtualization or platform virtualization allows multiple operating system instances to run concurrently on a single computer. This is a means of separating hardware from a single operating system. A hypervisor or Virtual Machine Monitor (VMM) is a piece of computer software that runs on host machine, which will allow you to create and manage the virtual machine on top of the host. The hypervisor virtualizes all resources (for example, processors, memory, storage, and networks) and allocates them to the various virtual machines that run on top of the hypervisor. In general, physical hardware that runs the hypervisor software is called the host machine and the virtual machine is called the guest operating system.

Consider an example of a computer that is running a production application server on Red Hat Enterprise Linux. The developer needs to test and implement new features. In a typical scenario without any virtualization, there will be dedicated physical hardware for the production and development environment. Virtualization allows you to run both production and development instances of your application in complete isolation from one another on the same physical hardware. As the virtualization hypervisor software sits between the guest and the hardware, it can control the guests' use of CPU, memory, storage, and network between these two environments.

Kernel-based Virtual Machine (KVM)

Kernel-based Virtual Machine is an open source hypervisor solution (http://www.linux-kvm.org/page/Main_Page) for Linux that supports x86, PowerPC, and S390 CPU architecture that contains virtualization extensions. KVM uses the hardware virtualization support of these processors and effectively turns your Linux kernel into a bare metal hypervisor. It supports a mixed workload of various guest operating systems that run your applications on Linux and Windows in order to host critical and noncritical applications. Many current Linux distributions ship KVM and the Red-Hat-included KVM hypervisor technology in a release of Red Hat Enterprise Linux Version 5 update 4 and its later release.

KVM outperforms other virtualization hypervisors in various virtualization scenarios, and it has top scores in the SPECvirt_2010 virtualization benchmark. It includes the overall top performance scores and the highest number of performant VMs running on a single hypervisor. KVM is free software that was released under the GPL, and it's a powerful open source hypervisor solution alternative to the VMware, Citrix Xen, and Hyper-V RHEV overview.

The RHEV platform is an enterprise-grade, centralized-management hypervisor for server and desktop virtualization. It's a complete virtualization management solution that provides fully integrated management of your virtual infrastructures. The RHEV platform includes two major components: Red Hat Enterprise Virtualization Manager, which is a centralized management server, and optimized KVM hypervisor software, which hosts the virtual machines.

Red Hat supports RHEV through the subscription model, which provides enterprise-ready solutions that can be confidently deployed to manage even your most mission-critical applications. Red Hat subscription gives you access to the Red Hat customer portal (https://access.redhat.com) and provides simple, integrated access to all features of your subscription. Users can open support tickets, read and download the documentation, and find useful information in the knowledge base.

RHEV is based on the KVM hypervisor and the upstream oVirt open virtualization management platform, which is a project started by Red Hat and released to the open source community (http://www.ovirt.org/Home). oVirt is the community-supported open source project. It will be the baseline of RHEV products, and it's very similar to RHEL, which is based on the Fedora distro.

Features of RHEV

With RHEV, you can virtualize even the most demanding application workloads with features including the following:

Host scalability: This supports a limit of up to 160 logical CPUs and 2 TB per host (platform capable of up to 4,096 logical CPUs / 64 TB per host)
Guest scalability: This supports up to 160 vCPU and 2 TB VRAM per guest
KSM memory over commitment: This allows administrators to define more RAM in their VMs than what is present in a physical host
Security: This supports SELinux and new sVirt capabilities, including Mandatory Access Control (MAC) for enhanced virtual machine and hypervisor security
Management: This provides centralized enterprise-grade virtualization management engines with a graphical administration console and programming interfaces
Live migration: This allows running virtual machines to be moved seamlessly from one host to another
High availability: This allows critical VMs to be restarted on another host in the event of hardware failure with three levels of priority
System scheduler: This provides system scheduler policies for load balancing to automatically balance the VM load among hosts in a cluster
Power saver: The power saver mode is used to consolidate VM loads onto fewer hosts during nonpeak hours
Maintenance manager: This allows you to move the hypervisor into the maintenance mode for any software or hardware updates of the hypervisor
Image management: This supports template-based provisioning, live virtual machine snapshots, and cloning new virtual machines from snapshots
Monitoring and reporting: This provides a suite of preconfigured reports and dashboards and creates your own ad hoc reports that enable you to monitor the system
OVF import/export: This allows you to import and export Open Virtualization Format (OVF) virtual machines into RHEV
V2V: This automates the conversion of the VMware or Xen virtual machine images into an OVF file for use within RHEV

Supported virtual machine operating systems

RHEV supports a wide range of Linux and Windows operating systems that can be virtualized as guest operating systems.

Note

Refer to http://www.redhat.com/resourcelibrary/articles/enterprise-linux-virtualization-support for information on the up-to-date guest support.

RHEV architecture

The RHEV platform comprises multiple components that work seamlessly together, as represented in the following diagram, and each component is explained in detail under the Components of RHEV section:

Components of RHEV

The RHEV platform consists of the following components:

Red Hat Enterprise Virtualization Manager (RHEV-M): This is a centralized management console with a graphical, web-based interface that manages your complete virtualization infrastructure, such as hosts, storage, network, virtual machines, and more, running on the physical hardware.
Red Hat Enterprise Virtualization Hypervisor (RHEV-H): RHEV hosts can be either based on full Red Hat Enterprise Linux 6 systems with KVM enabled (also called Red Hat Enterprise Linux Virtualization Hosts) or on purpose-built RHEV-H hosts. RHEV-H is a bare metal, image-based, small-footprint (less than 200 MB) hypervisor with minimized security footprint, also referred to as Red Hat Enterprise Virtualization Hypervisor.
What is the difference between these two? RHEV-H is like a live image that does not allow third-party applications, whereas the RHEL host is an operating system with KVM modules that allows any third-party software.
Virtual Desktop and Server Management Daemon (VDSM): This runs as the VDSM service on the RHEV hypervisor host that facilitates the communication between RHEV-M and the hypervisor host. It uses the libvirt (http://libvirt.org/) and QEMU service for the management and monitoring of virtual machines and other resources such as hosts, networking, storage, and so on.
Storage domains: This is used to store virtual machine images, snapshots, templates, and ISO disk images in order to spin up virtual machines.
Logical networking: This defines virtual networking for guest data, storage access, and management and displays network that accesses the virtual machine consoles.
Database platform: This is used to store information about the state of virtualization environment.
SPICE: This is an open remote computing protocol that provides client access to remote virtual machine display and devices (keyboard, mouse, and audio). VNC can also be used to get remote console access.
Authentication: This provides integration with external directory services such as Red Hat IPA and Active Directory Services for user authentication.
API support: RHEV v3.3 and higher supports the REST API, Python SDK, and Java Software Development Kit, which allow users to perform complete automation of managing virtualization infrastructure outside of a standard web interface of manager using own programs or custom scripts. Users can also use command-line shell utility to interact with RHEV-M outside of the standard web interface in order to manage your virtual infrastructure.
Admin/user portal: This is used for initial setup, configuration, and management. There is a power user portal, which is a trimmed-down version of the administration portal that is tailored for the end user's self-provisioning of virtual machines.

The hardware and software requirement of RHEV

The following section explains the minimal hardware and software requirements in order to install, set up, and run RHEV in your environment.

Red Hat Enterprise Virtualization Manager

In order to deploy and set up RHEV-M on a physical or virtual machine, the following are the minimum or recommended hardware prerequisites:

Minimum requirements:

A dual-core CPU
4 GB of RAM
25 GB local disk space
Network Interface Card with bandwidth of 1 GBps

Recommended requirements:

A quad-core CPU
16 GB of RAM
50 GB local disk space
Network Interface Card with bandwidth of 1 GBps

RHEV-M requires the Red Hat Enterprise Linux 6.3 server or higher. Install only minimal or basic server type during the installation in order to avoid package conflict while setting up the manager.

A valid Red Hat Network subscription uses RHN classic to access the following channels. It is highly recommended that you use the Red Hat subscription manager to subscribe to these relevant channels. However, the following channel names will vary if you use the subscription manager. In this book, we use RHN classic to register and subscribe to the following channels later during our manager setup:

Red Hat Enterprise Linux Server (v6 for 64-bit x86_64)
RHEL Server Supplementary (v6 64-bit x86_64)
Red Hat Enterprise Virtualization Manager (v3.3 x86_64)
Red Hat JBoss EAP (v6) for 6Server x86_64

The Red Hat Enterprise Virtualization Hypervisor host

One or two physical hosts act as virtualization hosts or RHEV-H. A minimum of two hypervisor hosts is required to demonstrate and test the live migration of virtual machines across hypervisor hosts.

Intel or AMD 64-bit supported hardware with virtualization extensions support of Intel VT or AMD-V enabled with following minimal compute requirements:

2 GB RAM
2 GB local disk space
One network interface with a bandwidth of 1 GBps

The recommended hardware for virtualization hosts always varies as per your requirement. Consider the following basic factors before sizing your hardware:

The number of guest operating systems, their application memory, and CPU requirements. For network-intensive application workloads, add multiple network interfaces and segregate the network traffic using RHEV's logical networks.
For less critical and non-disk I/O-intensive applications, use local storage, and in this case, extend the internal storage size of virtualization hosts in order to store the virtual machine images as per your requirement. However, keep in mind that the use of local storage will prevent other features such as live migration of virtual machines to other hosts.
For high transnational database workloads, use the NAS/SAN storage with a dedicated network interface in the case of NAS and FC for SAN.
Virtualization hosts must run Version 6.3 or higher of either the RHEV hypervisor host or Red Hat Enterprise Linux Server as a host.

The Red Hat Enterprise Virtualization Manager client

In order to access the manager, you need the following supported clients and browsers:

Mozilla Firefox 17 or higher is required to access both portals on Red Hat Enterprise Linux.
Internet Explorer 8 or higher is required to access the user portal on Microsoft Windows. Use the desktop version and not the touchscreen version of Internet Explorer 10.
Internet Explorer 9 or higher is required to access the administration portal on Microsoft Windows. Use the desktop version and not the touchscreen version of Internet Explorer 10. It's possible to access the manager portal from other browsers, but it's not tested and supported. Similarly, tablet and touchscreen versions of browsers are also not supported and tested at the time of writing this book.

Install a supported SPICE client in order to access virtual machine consoles. Check the Red Hat Enterprise Virtualization Manager release notes to see which SPICE features your client supports.

Storage

You need a storage type of NFS, ISCSI, SAN, POSIX, Red Hat Storage (GlusterFS), or local storage for data domains to store virtual machine images. The NFS system is required in order to store your ISO library and to export and import virtual machines for complete image backup and restoration of virtual machine images.

Directory services (optional)

While setting up RHEV-M, the RHEV-M installer script will create its own internal admin user for the initial configuration and setup. To add more users, you need to attach the manager to one of the supported directory services:

Active Directory Red Hat Identity Management (IdM)
Red Hat Directory Server 9 (RHDS 9)
OpenLDAP

Networking and Domain Name Service

For the host networking and fully qualified domain name resolution, you need the following:

A static IP address for RHEV-M and for each hypervisor host management network.
A DNS service that can resolve both forward and DNS entries for those static IP addresses.
An optional existing DHCP server that can address the network address for the virtual machine.

Virtual machines

We need installation images in order to create virtual machines and their valid license or subscription entitlement for each operating system. We will use these ISO images and later upload them to the ISO domain in order to use them as an installation media that deploys the operating system on a virtual machine.

Firewall Requirements

The RHEV infrastructure requires that the network traffic on a number of ports be allowed through the firewall. The following is the list of required ports that are to be opened on the firewall across various RHEV components.

Virtualization manager firewall requirements

RHEV-M requires the following ports be opened in order to allow network traffic through the system's firewall:

Source	Destination	Port/Protocol	Purpose
The hypervisor host	RHEV-M	ICMP	RHEV-M verifies the hypervisor's reachability via ICMP after the initial host registration
The remote client	RHEV-M	22/TCP	To provide SSH access to the manager
Admin / User portal clients / Hypervisor host	RHEV-M	80 and 443/TCP	To access the admin and user portal from remote clients

Note

If you plan to use the NFS ISO storage domain on the same box as the running RHEV-M in order to store your ISO library to create virtual machines, please open TCP port 2049 for NFSv4.

Virtualization host firewall requirements

The Red Hat Enterprise Virtualization Hosts require the following ports be opened in order to allow the network traffic through the system's firewall:

Source	Destination	Port/Protocol	Purpose
RHEV-M	Hypervisor Hosts	22	To secure shell access
Admin /User portal clients	Hypervisor Hosts	From 5900 to 6411/TCP	Used for Spice/VNC console access
Hypervisor Hosts	Hypervisor Hosts	16514/TCP	Used for libvirt virtual machine migration
Hypervisor Hosts	Hypervisor Hosts	From 49152 to 49216/TCP	Used for virtual machine migration and fencing
Hypervisor Hosts / RHEV-M	Hypervisor Hosts	54321/TCP	To provide VDSM communication with manager and hypervisors

Directory server firewall requirements

The following ports are to be opened if you wish to integrate RHEV-M with directory services for user authentication:

Source	Destination	Port/Protocol	Purpose
RHEV-M	Directory server	88 and 463/(TCP/UDP)	Used for the Kerberos authentication
RHEV-M	Directory server	389 and 636/TCP	Lightweight Directory Access Protocol (LDAP) and LDAPS over SSL

Remote database server firewall requirements

The following ports are to be opened if you wish to use the remote PostgreSQL database instance with RHEV-M:

Source	Destination	Port/Protocol	Purpose
RHEV-M	Remote PostgreSQL database server	5432/(TCP and UDP)	Used as a default port for PostgreSQL database connections

User accounts and groups

The following users and groups are created by the RHEV-M setup tool in order to support virtualization on the manager system. If existing UIDs and GIDs on the host conflict with the default values used during the VDSM and QEMU installation, a conflict occurs.

Users	Group
VDSM (UID: 36) oVirt (UID: 108)	KVM (GID: 36) oVirt (GID: 108)

The following users and groups are created by default on the hypervisor when installing VDSM and QEMU packages. If existing UIDs and GIDs on the host conflict with the default values used during the installation, a conflict occurs.

Users	Group
VDSM (UID: 36) QEUM (UID: 107) Sanlock (UID: 179)	KVM (GID: 36) QEUM (GID: 107)

Note

RHEV 3.3 supports a self-hosted engine of RHEV-M, which enables RHEV-M to be run as a virtual machine on the hypervisor hosts it manages in an HA configuration. This will reduce the dependency on the dedicated physical or virtual hardware that hosts your RHEV-M instance.

For more information, refer to Red Hat Enterprise Virtualization Manager 3.3 Release notes at https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Virtualization/3.3/html-single/Manager_Release_Notes/index.html.

Summary

In this chapter, we discussed the basic concept of virtualization and were introduced to the Linux kernel virtual machine. We then moved further with an introduction to Red Hat Enterprise Virtualization and its relation to KVM. Then, we learned about the detailed architecture, components, and hardware and software requirements of Red Hat Enterprise Virtualization for better planning in order to design your first Red Hat Enterprise Virtualization infrastructure.

In the next chapter, we will learn how to install and configure RHEV Manager and hypervisor hosts. This will also explain how to manage your virtual infrastructure from the admin web interface and access the reporting from the report portal.