Now let talk about High Availability for SQL Server.
SQL Server 2005 can do active/active and active/passive clustering.
In active/passive - one node will hold the resources and provide services to application/user. The passive node will act as standby unit and only use when failover.
In active/active - both node will hold the resource and serve the application simultaneously. In sql server use need to install into different instance group.
The following actions are needed to configure active/active clustering for sql server:
1. Build Active/Passive Windows cluster for all nodes with checking cluster disk resource.
2. Configure MSDTC
3. Install one instance on Node 1. Set preferred owner for the Instance Group to Node 1
4. Install another instance on Node 2. Set preferred owner for the Instance Group to Node 2.
5. Test using Studio Management.
Hope this info assist you in configure sql server clustering.