HP Integrity rx5670 Windows Integrity Cluster Installation and Configuration G - Page 7

Introduction Clustering overview Clustering overview A cluster is a group of individual servers, or nodes, configured to appear as a single, virtual server. The nodes making up the cluster generally run a common set of applications. They are physically connected by cables, and programmatically connected by the clustering software. Together these nodes appear as a single system to both users and applications. Clusters provide the following advantages over stand-alone servers: • High availability-Clusters are designed to avoid single points-of-failure. Applications can be distributed over more than one node, achieving a high degree of parallelism and failure recovery. • Manageability-Clusters appear as a single system to end users, applications, and the network, while providing a single point of control for administrators, either locally or remotely. • Scalability-You can increase the cluster's computing power by adding more processors or computers. Applications can also be scaled according to need as a company grows. Because of the inherent redundancy of a hardware and software in a cluster, businesses are protected from system down-time due to single points of failure, power outages, natural disasters, and even during routine system maintenance or upgrades. In addition, clusters help businesses eliminate penalties and other costs associated with not being able to meet the Service Level Agreements they are contracted to provide. A cluster is similar to a general distributed system, except that it provides the following additional capabilities: 1. Every node has full connectivity and communication with the other nodes in the cluster through the following methods: • Hard disks on a shared bus-One or more shared buses used for storage. Each shared bus attaches one or more disks that hold data used to manage the cluster. Cluster service provides a dual-access storage model whereby multiple systems in the cluster can access the same storage. • Private network-One or more private networks, or interconnects, carry internal cluster communication only (called "heartbeats"). At least one private network is required. • Public network-One or more public networks can be used as a backup for the private network and can be used both for internal cluster communication and to host client applications. Network adapters, known to the cluster as network interfaces, attach nodes to networks. 2. Each nodes tracks cluster configuration. Every node in the cluster is aware when another system joins or leaves the cluster. 3. Every node in the cluster is aware of the resources that are running locally as well as the resources that are running on the other nodes. Chapter 1 7