This chapter discusses the procedure to configure Volume Replicator in a VCS environment. Cluster Server (VCS) connects or clusters, multiple, independent, systems into a management framework for increased availability. Each system, or node, runs its own operating system and cooperates at the software level to form a cluster. VCS links commodity hardware with intelligent software to provide application failover and control. When a node or a monitored application fails, other nodes can take predefined steps to take over and bring up services elsewhere in the cluster, thus providing an image of a single system to the client.

Volume Replicator can enable applications to be highly available at geographically-separated sites, by configuring them in a VCS cluster. A VCS cluster is configured at a Primary site as well as the Secondary site. In this case, the servers where the application is running can be referred to as the source or Primary cluster and the servers to which the data is replicated, can be referred to as the destination or Secondary cluster. The failover between these sites is enabled with the help of agents that are explained in this chapter. The VCS Agent for Volume Replicator is installed and configured on each VCS node to enable Volume Replicator RVGs to failover between nodes, in a VCS cluster. Different service groups are created to represent the application and replication-related resources. A dependency is set between the application and replication service groups.

Local clustering provides local failover for each site or building. Campus and replicated data cluster configurations offer some degree of protection against disasters affecting limited geographic regions. But, these configurations do not provide protection against large-scale disasters such as major floods, hurricanes, and earthquakes that cause outages for an entire city or region. Such an outage can affect the entire cluster. In such situations, you can ensure data availability by migrating applications to remote clusters located considerable distances apart using global clustering.

In such a global cluster, if an application or a system fails, the application is migrated to another system within the same cluster. If the entire cluster fails, the application is migrated to a system in another cluster. This is known as a wide-area failover. If the configuration consists of a Bunker setup, and the entire Primary site fails, then during failover to another system global clustering ensures that the new system is synchronized with pending updates from the Bunker node.

Clustering on a global level requires replicating application data to the remote site. Thus, Volume Replicator along with VCS can be used to provide an effective disaster recovery solution.