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XEN Cluster

XEN Cluster Project

This section provides information about my XEN cluster with share storage that I currently use at home. It consists of two machines with identical hardware and software. A two node cluster utilizing XEN, DRBD and Heartbeat. I will here describe in detail how I did it.

Why?

A friend of mine always asks for the reason for doing things. Why? Why are you doing this? Especially this project can seem like a stupid thing to do in your home. Why would I need High Availability (HA) XEN cluster with shared storage?

I actually had several reasons. The main one being the lack of safe storage, especially for pictures and documents. Until now I had everything stored on our desktop computer, so in case of a crash I could lose everything. I had also a mini-itx server running Asterisk, being a media server and VPN server. This server was without redundancy and was also getting slow as I tend to install more and more things. So I thought that the best idea was to build a cluster with shared storage to get the redundancy, and then run virtual servers to be able to separate Asterisk from my file server.

What?

I decided to use XEN for my virtual environment, being open source and seemed to have the best features. With XEN you normally have virtual machines (VM) running in, what is called, para-virtualized mode, as compared to fully-virtualized. But with newer chipsets and CPUs from AMD and Intel built with extensions for virtualization, XEN supports both modes. Intel-VT or AMD-V are the names of this technology. I wanted to be able to run both modes as fully-virtualized makes it possible to install a VM directly from an iso image, CD or DVD. I compared Intel-VT and AMD-V and made the decision to go with AMD-V. It seemed as Intel did not properly support or had the correct implementation of all features, causing certain VM installations to fail. And another factor was the price. AMD was way cheaper than Intel.

Last Updated on Saturday, 05 September 2009 11:29
 

XEN cluster news

2009-10-10

Had no time to do any enhancements to this installation except for performing regular Linux system updates. I actually believe that some of these updates have broken the heartbeat functionality of my system. A while back I noticed I started to have issues just performing a standard reboot of one node. When the node comes back up again, the VMs are active on both nodes. It has forced me now to switch off heartbeat just to avoid any data corruption. Have seen posts with similar issues so it is possible that my setup is not compatible with the latest version of heartbeat.

Would like to try a reinstall on the latest Ubuntu version, would be a great test to do while maintaining my live data.

Would also like to try the new free version on XenServer from Citrix. I know it is not open source, but it would be great for comparison. Smile

2008-10-25

I bought a APC UPS which is currently feeding both of the two Dom0 nodes. I still have to install and configure the scripts so I can do automatic shutdowns in case of power failures.

Added new material describing how to extend a disk in a DomU that is based on DRBD on top of LVM. Please read more about it here: XEN extend DomU disk

2008-08-21

Added info in the HowTo about a bug in the xendomains script. Also added a section for troubleshooting at the end of the HowTo.

2008-08-16

I moved my Trixbox(Asterisk Linux distribution) installation from a physical machine to a virtual machine. I didn't migrate the system from a physical installation to a VM, I did a new installation of Trixbox on a VM and then copied the configuration for Asterisk.

I first installed Trixbox as HVM and later converted it to a PVM. Please read more about it here: Convert Trixbox HVM to PVM

Last Updated on Saturday, 10 October 2009 14:36
 

XEN Cluster HowTo

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.

2011-02-27: The setup in Ubuntu was very stable and I had initially very few problems. I ran into some trouble later on when it turned out that my heartbeat in combination with XEN was negatively effected by some system updates. Never had time to resolve it so I eventually switch off heartbeat as it was just causing issues.
Instead I have started with a new install consisting of Debian Squeeze and XEN version 4. I'm migrating the data upgrading one node at the time. Documenting the migration phase and will publish it together with a fresh install guide.

Last Updated on Tuesday, 01 March 2011 21:55 Read more...
 
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