Server clustering technology, which we have been discussing throughout our series (within the context of Windows Server 2003 R2), delivers high availability by emulating a variety of features using the concept of virtualized resources. While the majority of these resources correspond to specific physical or logical components (such as disk volumes, IP addresses and network names), several offer much more flexibility in terms of the functionality they represent. This flexibility, however, comes at the price of complexity associated with their implementation. This article will focus on such resources, which include Generic Service, Generic Application and Generic Script.
Each of these three resource types increases the resiliency of services, applications and software components, which are not available in the cluster-aware format from vendors. Cluster awareness implies use of specific cluster API calls when managing their behavior, which, in turn, facilitates such cluster-specific actions as failover or failback. Although the capabilities of Generic Service and Generic Application Resources are to some extent limited, compared to Generic Script, they are worth exploring in more detail, since the high availability benefit they provide can be realized via a fairly simple configuration.
