Designing High-Availability for Xen Virtual Machines with HP Serviceguard for Linux

Executive Summary

This white paper describes how to integrate Xen Dom0 hosts into a Serviceguard for Linux (SG/LX)

cluster, and how to configure Xen Virtual Machines (VMs) as SG/LX packages. It also makes

recommendations for eliminating single points of failure and provides pointers to other useful

documents.

Introduction

Virtual machines on Xen are increasingly being deployed for server consolidation and flexibility.

Virtual machine technology allows one physical server to emulate multiple servers, each capable of

running its own operating system (OS) concurrently with other virtual servers. The virtualization layer,

also known as the hypervisor, abstracts the physical resources so that each instance of an OS

appears to have its own network and storage adapters, processors, disks, and memory, when in fact

they are virtual instances.

A significant single point of failure for Xen virtual machines is the physical hardware which runs the

Xen dom0 hypervisor. Dom0, or domain zero to expand the abbreviation, is the first domain started

by the Xen hypervisor on boot. It has special privileges, such as being able to cause new domains to

start, and being able to access the hardware directly. A failure of the Xen hypervisor or the server it is

running on can bring down all of the Xen virtual machines running on that server. One can protect the

Xen virtual machines from these failures by using SG/LX clustering to make the Xen hypervisor highly

available.

This document describes how to configure an SG/LX cluster consisting of multiple Xen dom0 hosts.

The Xen virtual machines (VMs) can then be configured as SG/LX packages. In the event of a failure,

or to maintain application availability while performing online upgrades and maintenance, a Xen

virtual machine protected within a Serviceguard for Linux package can be restarted on the same

node, or on another node in the cluster. The other nodes would also be Xen dom0 hypervisors

running Serviceguard for Linux.

This solution protects the Xen virtual machine from the following failures:

• Failure of a Xen virtual machine

• Failure of networking

• Failure of storage

• Failure of the physical machine (running as Xen dom0 host)

Scope

This document describes how to provide high availability for Xen virtual machines using Serviceguard

for Linux running on multiple Xen dom0 hosts. See the Support Requirements section for a list of

supported versions of Xen Server and Linux distributions. As new versions of Xen server or Linux

distributions are certified, this whitepaper and the Serviceguard for Linux Certification Matrix will be

updated accordingly. The most recent version of the Serviceguard for Linux Certification Matrix can

be found at www.hp.com/go/sglx/info

, in the Solution planning section.

Note: Serviceguard for Linux is currently certified to run on Xen dom0 hosts, not on Xen virtual

machine guests. Applications running on the dom0 host, including the virtual machines can be

configured to run as SG/LX packages. This configuration provides high availability to host based

applications and virtual machines.