1.1 Xen Cluster Architecture

The following diagram shows how Cloud Manager 2.x interacts with a SLES HAE cluster. To manage VMs in the cluster, the Cloud Manager Orchestration Server needs to communicate with the cluster stack. This communication happens through an Orchestration Agent, which the administrator configures as a cluster resource using a special configuration script.

When configured, the SLES HAE cluster chooses which cluster node the Agent runs on, just as it does for any other cluster resource. To make sure that the agent has a consistent IP address, the configuration script sets up an IP address resource in a cluster resource group, along with the cluster resource for the Orchestration Agent. If the Orchestration Agent fails over to another cluster node, its cluster IP address moves with it.

Figure 1-1 Cloud Manager Interaction with a SLES HAE Cluster

Assuming that a SLES HAE cluster is correctly installed and configured, setting up the additional cluster resources is relatively uncomplicated. The Orchestration Server administrator installs and configures the Orchestration Agent on each node in the cluster. In a standard agent configuration, this launches the agent, but because this configuration is for a high availability environment, the agent is not started.

To configure the cluster resources for the agent, the administrator runs a special configuration script on a single node in the cluster. This script needs to be run only once. It creates the cluster resource group, a cluster resource for an IP address, and a cluster resource for the Orchestration Agent. The script then starts the cluster resource group in the cluster. Following this configuration, the Orchestration Agent runs in the cluster as a cluster resource where it can be used by the Orchestration Server to communicate with the cluster stack to facilitate VM management in the cluster.