Compaq ProLiant 6500 Deploying the ProLiant Cluster for NetWare 4.2 - Page 3

'HSOR\LQJ WKH 3UR/LDQW &OXVWHU IRU 1HW:DUH   Clustering Overview The computer industry has been using a wide range of solutions to reduce system downtime for years. Many of these solutions have been both expensive and difficult to setup and maintain. Historically, only mission-critical applications, such as those controlling stock exchange trading floors and aerospace missions, were deemed important enough to justify proprietary clustering solutions. However, as the presence of computer systems in day-to-day business operations has increased, the amount of acceptable downtime has decreased. Today, a new class of applications exists; business-critical applications key to business success but not significant enough to justify the high price tag of a proprietary clustering solution. More and more applications are becoming businesscritical. Computer applications are becoming more widely deployed and their failure causes immediate lost revenue, decreased productivity, and, potentially, dissatisfied customers. Poised to meet the increased demands, clustering technology is entering mainstream industrystandard computing. As a result, new clustering solutions, using industry-standard hardware and software, provide key clustering features at a lower price than proprietary clustering systems. Clusters Defined Traditionally, clustering is the integration of software and hardware that enables a set of loosely coupled servers and storage to operate as a single system, presenting a single entity to clients. As a cluster, the group of servers and storage offers a level of availability greatly exceeding the reliability of a standalone server. This translates into increased performance and greater data availability for end users. The ProLiant Cluster for NetWare 4.2 extends the definition by providing the same level of reliability while maintaining distinct network entities for each server. By defining distinct server identities, tasks and users may be distributed easily between the distinct servers. With the focus for clustered systems being reliability, the ProLiant Cluster for NetWare 4.2 delivers again with automatic failover of all network resources and responsibilities in the event of a failure. Should one server in the cluster lose access to the shared storage and network, the other server assumes the responsibilities of the downed server. Causes of Downtime Computer downtime is the period of time that a computer system cannot meet the requests of its users. The following are the leading causes of downtime: • Planned service - In a cluster, a single server can be taken offline, while the other server takes on the workload of the downed server. This allows planned service to occur with only minimal interruption to the overall system operation. • Software failures - Because clustering provides a mechanism to automatically fail over processes when a discernible software failure occurs, the overall system operation can continue with only minimal interruption. • Hardware failures - If it is determined that a hardware failure will result in system downtime, the cluster will fail over processes from one node to another, allowing the overall system operation to continue with little interruption. 0096-0699-A