Choosing Applications for Failover Clusters

Many applications can run on failover clusters, but it is important to choose and test those applications wisely. Although many can run on failover clusters, the application might not be optimized for clustering or supported by the software vendor or Microsoft when deployed on Windows Server 2008 R2 failover clusters. Work with the vendor to determine requirements, functionality, and limitations (if any). Other major criteria that should be met to ensure that an application can benefit and adapt to running on a cluster are the following:

» Because clustering is IP-based, the cluster application or applications must use an IPbased protocol.

» Applications that require access to local databases must have the option of configuring where the data can be stored so a drive other than the system drive can be specified for data storage that is separate from the storage of the application core files.

» Some applications need to have access to data regardless of which cluster node they are running on. With these types of applications, it is recommended that the data is stored on a shared disk resource that will failover with the Services and Applications group. If an application will run and store data only on the local system or boot drive, the Node Majority Quorum or the Node and File Share Majority Quorum model should be used, along with a separate file replication mechanism for the application data.

» Client sessions must be able to reestablish connectivity if the application encounters a network disruption or fails over to an alternate cluster node. During the failover process, there is no client connectivity until an application is brought back online. If the client software does not try to reconnect and simply times out when a network connection is broken, this application might not be well suited for failover or NLB clusters.

Cluster-aware applications that meet all of the preceding criteria are usually the best applications to deploy in a Windows Server 2008 R2 failover cluster. Many services built in to Windows Server 2008 R2 can be clustered and will failover efficiently and properly. If a particular application is not cluster-aware, be sure to investigate all the implications of the application deployment on Windows Server 2008 R2 failover clusters before deploying or spending any time prototyping the solution.

If you’re purchasing a third-party software package to use for Windows Server 2008 R2 failover clustering, be sure that both Microsoft and the software manufacturer certify that it will work on Windows Server 2008 R2 failover clusters; otherwise, support will be limited or nonexistent when troubleshooting is necessary.

Source of Information : Sams - Windows Server 2008 R2 Unleashed (2010)