PUBLIC MARKS with tags cluster & xen

In order to be able to do a live migration of a Xen guest from one cluster member to another, some sort of shared storage is required. As the Xen guest won’t run on more than one cluster member at a time, a cluster filesystem is not required. That is, as long as you configure Xen to access the Xen guest by a physical device, not a file.

I have tried to run both Debian Etch and Ubuntu 8.04 Server on the cluster nodes, in Dom0. I started my tests with Debian, but I had some issues with slow samba performance in one VM that I couldn't fix so I decided to try Ubuntu Server, for the first time. Both installation went OK, the main difference was that I used mainly source code in Debian, but only packages in Ubuntu. I actually ran into more problems with Ubuntu due to some early bugs in the 8.04 release, will describe them below as I go along. And I have still to prove that running this setup in Ubuntu is stable.

OpenNebula transforms a physical cluster into a flexible virtual infrastructure which dynamically adapts to the changing demands of a service workload. OpenNebula leverages existing virtualization platforms to create a new virtualization layer between the service and the physical infrastructure. This new layer supports the execution of the services on a physical cluster, extending the benefits of VMMs (Virtual Machine Monitors) from a single physical resource to a cluster of resources. OpenNebula effectively decouples a server (deployed as a pre-configured VM) not only from the physical infrastructure but also from its physical location.

By default, migrating a Xen Virtual Machine (VM) resource causes it to shutdown on the current node and restart on the new one. Once you configure a Xen VM within the High Availability Storage Infrastructure (HASI), how do you configure the Xen VM resource to live migrate among the cluster nodes?

The idea behind the whole set-up is to get a High availability two node Cluster with redundant data. The two identical Servers are installed with Xen hypervisor and almost same configuration as Cluster nodes. The configuration and image files of Xen virtual machines are stored on drbd device for redundancy. Drbd8 and OCFS2 allows simultaneous mounting on both nodes, which is required for live migration of xen virtual machines. This Article describes Heartbeat2 Xen cluster Using Ubuntu (7.10) OS, drbd8 and OCFS2 (Ver. 1.39) File system. Although here Ubuntu is used it can be done in almost same way with Debian

The idea of using virtual machines to build high available clusters is not new. Some software companies claim that virtualization is the answer to your HA problems, off course that's not true. Yes, you can reduce downtime by migrating virtual machines to another physical machine for maintenance purposes or when you think hardware is about to fail, but if an application crashes you still need to make sure another application instance takes over the service. And by the time your hardware fails, it's usually already too late to initiate the migration.

In this article, I briefly introduce the concepts of Xen virtualization and Linux clustering. From there, I show you how to set up multiple operating systems on a single computer using Xen and how to configure them for use with clustering. I should point out that a cluster implemented in this manner does not provide the computational power of multiple physical computers. It does, however, offer a way to prototype a cluster as well as provide a cost-effective development environment for cluster-based software. Even if you're not interested in clustering, this article gives you hands-on experience using Xen virtualization.

This Article describes Heartbeat2 Xen cluster Using Ubuntu (7.10) OS, drbd8 and OCFS2 (Ver. 1.39) File system. Although here Ubuntu is used it can be done in almost same way with Debian Idea The idea behind the whole set-up is to get a High availability two node Cluster with redundant data. The two identical Servers are installed with Xen hypervisor and almost same configuration as Cluster nodes. The configuration and image files of Xen virtual machines are stored on drbd device for redundancy. Drbd8 and OCFS2 allows simultaneous mounting on both nodes, which is required for live migration of xen virtual machines.

This guide is the first of a series in which I give you detailed step-by-step instructions on how to build a virtual cluster with Xen. The cluster thus built might not be appropriate for your case, and does reflect the author's preferences and/or needs, but if you are new to clusters or Xen, it will hopefully help you get started with both. The goal is to start it simple and then add more complexity as we progress, so in this first guide I show you how to get do the basics: * A Xen installation, the creation of 5 virtual machines (one to act as the master and four slaves), * Shared storage through NFS, * The network configuration on which to build the virtual cluster. The network structure of this first attempt will be very simple, the master having two network cards, one to the outside world and the other one connected through a switch to the slaves.

We have implemented a 2-node HA Xen cluster, which consists of two physical machines (hosts,) and runs several virtual servers (guests) each, for our company's internal services (mail, web applications, development, etc.) When one host gets down unexpectedly, the other host physically kills it (STONITH - power down or reset) and then takes over all the guests the failed host was running. When we want to shutdown a host machine for maintenance (to replace a fan, add disk or memory, etc.), we just type the usual shutdown command, and the guests are automatically live-migrated to the other host. Since the guest servers keep running throughout the migration process, except for the less than a second pause, users would never even notice the event.

Ganeti is a virtual server management software tool built on top of Xen virtual machine monitor and other Open Source software. However, Ganeti requires pre-installed virtualization software on your servers in order to function. Once installed, the tool will take over the management part of the virtual instances (Xen DomU), e.g. disk creation management, operating system installation for these instances (in co-operation with OS-specific install scripts), and startup, shutdown, failover between physical systems. It has been designed to facilitate cluster management of virtual servers and to provide fast and simple recovery after physical failures using commodity hardware.

Ganeti is a cluster virtualization management system based on Xen. In this tutorial I will explain how to create one virtual Xen machine (called an instance) on a cluster of two physical nodes, and how to manage and failover this instance between the two physical nodes.