2.12. Configuring Virtual Machines in a Clustered Environment

When you configure your cluster with virtual machine resources, you should use the rgmanager tools to start and stop the virtual machines. Using xm or virsh to start the machine can result in the virtual machine running in more than one place, which can cause data corruption in the virtual machine.
To reduce the chances of administrators accidentally "double-starting" virtual machines by using both cluster and non-cluster tools in a clustered environment, you can configure your system as follows:
  • Ensure that you are using the rgmanager 2.0.52-1.el5_4.3 or later package release.
  • Store the virtual machine configuration files in a non-default location.
Storing the virtual machine configuration files somewhere other than their default location makes it more difficult to accidentally start a virtual machine using xm or virsh, as the configuration file will be unknown out of the box to libvirt or the xm tool.
The non-default location for virtual machine configuration files may be anywhere. The advantage of using an NFS share or a shared GFS or GFS2 file system is that the administrator does not need to keep the configuration files in sync across the cluster members. However, it is also permissible to use a local directory as long as the administrator keeps the contents synchronized somehow cluster-wide.
In the cluster configuration, virtual machines may reference this non-default location by using the path attribute of a virtual machine resource. Note that the path attribute is a directory or set of directories separated by the colon ':' character, not a path to a specific file.
For more information on the attributes of a virtual machine resources, refer to Table C.23, “Virtual Machine”.