Clustering gives your application or database the chance to live on if your primary hardware fails. In a two-node cluster, both nodes of the cluster have access to the same back-end storage, be it locally attached SCSI or a storage area network. The cluster service is running on both nodes, so if one node fails, the storage resources are moved, automatically, to the other node and the application or SQL instance starts on the 2nd node. Limitations of the Microsoft operating system prevent both nodes from being able to access the storage simultaneously. Given that, the failover does create an outage of 5 to 15 seconds. That doesn't usually bother a properly coded application, though.
With the benefits also come the risks. A cluster adds a level of complexity not found in a standalone server. Simple maintenance tasks are much more complicated. Troubleshooting is a nightmare.
But if your application requires 24x7 access, then clustering elimates the single point of failure in the server.
Re: Cluster gives you high availability - in theory
Thaks for your information but i want to know more cos after i read some paper about clustering i get information that cluster have some technique such as k-clustering but i not understand basic concept about it. About ur answer yesterday i get info about clustering in microsoft.
My udergraduate task is built to make software implementation clustering with one of some technique clustering.