A Microsoft SQL Server Cluster is simply a collection of two or more physical servers. These servers or "nodes," have the same access to shared storage and provides the resources required to store the database files. Each of the nodes talks to one another via a network. If one node does not communicate to the other node in the cluster the secondary node will take ownership.
There are two types of clustering: Active/Active or Active/Passive.
In an Active/Active cluster there will be two or more nodes, each one "owning" an instance of Microsoft SQL Server. If one node fails, the instance it owns would fail over to the other node, running alongside (and contending for resources with) the other instance. Each copy of SQL Server acts independently. If one of the SQL Servers in the cluster should fail, then the failed instance of SQL Server wills failover to the remaining server. This means that both instances of SQL Server will be running on one physical server, instead of two. As you can imagine, if two instances have to run on one physical server, performance can be affected, especially if the server's have not been sized appropriately.
In an Active/Passive setup, at least one node is not the owner of an instance of SQL Server. It is "passive" and only exists to accept a failover of a node hosting a SQL instance in the event of a failover. From a performance perspective, this is the better solution. On the other hand, this option makes less productive use of your physical hardware, which means this solution is more expensive.
Windows Server 2008 and Microsoft SQL Server 2008 Enterprise Edition allows up to sixteen nodes. The current MS policy is, Active node need to be licensed and not the passive node.
Create new SQL Server Failover Cluster
To create new SQL Server Failover Cluster, please look at the MSDN guideline.
For disaster recovery of SQL server
Posted by: MR. JOYDEEP DAS