HP Integrity rx5670 Windows Integrity Cluster Installation and Configuration G - Page 13

NOTE NOTE Introduction Cluster terminology Resource state changes can occur either manually (when you use Cluster Administrator to make a state transition) or automatically (during the failover process). When a group is failed over, the states of each resource are altered according to their dependencies on the other resources in the group. Resource dependencies A dependency is a reliance between two resources that makes it necessary for both resources to run on the same node (for example, a Network Name resource depending on an IP address). The only dependency relationships that Cluster service recognizes are relationships between resources. Cluster service cannot be told, for example, that a resource depends on a Windows 2003 service; the resource can only be dependent on a resource representing that service. Groups Groups are a collection of resources to be managed as a single unit for configuration and recovery purposes. Operations performed on a group, such as taking it offline or moving it to another node, affect all resources contained within that group. Usually a group contains all the elements needed to run a specific application, and for client systems to connect to the service provided by the application. If a resource depends on another resource, each of the resources must be a member of the same group. In the example of the file share resource, the group containing the file share must also contain the disk resource and network resources such as the IP address and NetBIOS name to which clients connect to access the share. All resources within a group must be online on the same node in the cluster. During failover, entire groups are moved from one node to another in the cluster. A single resource cannot fail from one node to another. Quorums Each cluster has a special resource known as the quorum resource. The quorum provides a means for arbitration leading to node membership and cluster state decisions. Only one node at a time may own the quorum. That node is designated as the primary node. When a primary node fails over to a backup node, the backup node takes ownership of the quorum. The quorum resource also provides physical storage to maintain the configuration information for the cluster. This information is kept in the quorum log, which is simply a configuration database for the cluster. The log holds cluster configuration information such as which servers are part of the cluster, what resources are installed in the cluster, and what state those resources are in (for example, online or offline). By default the quorum log is located at \MSCS\quolog.log. Quorums are only used in the Microsoft Cluster Service known as Server Cluster (they are not used in Network Load Balancing). Therefore, references to quorums throughout the remainder of this document apply to Server Clusters only. Chapter 1 13