Maximizing Application Availability With Microsoft Cluster Services in a SAN Environment
For many years now, clusters of computer servers have been used in data centers to provide non-stop computing resources for mission-critical applications. With the recent emergence of newer, "always on" applications such as e-commerce and e-mail, the number of applications that require 24x7 server availability is steadily increasing. As a result, many IT organizations have standardized on clusters to achieve both higher application uptime and rapid recovery from the hardware and/or software failures that inevitably occur in any computing environment. As clustering has become more popular, there has also been a pronounced market shift from using traditional mainframe computers to service key applications to using clusters of lower cost Open System servers running the UNIX and Windows operating systems. In fact, today it is not uncommon to see IT shops that have deployed 20 or more clusters of Open System servers. In addition, many data centers are now constructing networks of clusters, using these multiple sets of clustered servers to replace their mainframe systems.
For IT shops with Windows environments, perhaps the most common cluster implementation used today is the Microsoft Cluster Server (often known as "MSCS"). Modern cluster implementations like MSCS depend on shared access to volumes of data stored on disk drives, where multiple servers clustered together must be able to access and share the same information. To satisfy this requirement, Fibre Channel Storage Area Networks have proven to be an ideal choice for providing shared data access to clustered servers, due to factors such as Fibre Channel's high bandwidth for data throughput and the elimination of many cable length limitations. However, there are some anomalies when using MSCS in Fibre Channel SAN environments. Left unaddressed, these anomalies can significantly affect the day-to-day use of clustered servers by degrading their performance and greatly limit the ability to scale the environment in response to business requirements. This paper describes the operational effects of using MSCS in a Fibre Channel SAN with multiple server clusters, and how StoreAge SVM™ can remove the negative effects, improve performance, and deliver a lower total cost of ownership than would otherwise be possible.