So who can tell me what clustering is? Who can tell me which types of clustering there are for SQL, what they mean, support and do? It isn’t that easy is it?. I found a great site with a nice explanation and some images to make it all clear to you guys. I copied some info from them and pasted it below:

http://www.sql-server-performance.com/rn_sql_server_clustering_2000_to_2005_1.asp

 

Clustering:

Clustering can be best described as a technology that automatically allows one physical server to take over the tasks and responsibilities of another physical server that has failed.

Active / Passive SQL Clustering
An Active/Passive, or Single Instance cluster, refers to a scenario where only one instance of SQL Server is running on one of the physical node in the cluster, and the other physical node does nothing, other then waiting to takeover should the primary node fail, or a manual failover for maintenance.

Active / Active SQL Clustering
An Active/Active SQL Server cluster means two separate SQL Server instances are running on both nodes of a two-way cluster. Each SQL Server acts independently, and users see two different SQL Servers instances. If one of the SQL Servers in the cluster should fail, then the failed instances of SQL Server will failover to the remaining server. This means that then both instances of SQL Server will be running on one physical server, instead of two.

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You might think why do we need this info, or why is this guy typing information I already know? Well I have noticed that a lot of people don’t know the facts and mix up things easily. This info will be important when you want to deploy Microsoft CRM 3.0 on for example an Active/Active SQL Cluster. You have to know if this configuration will be supported or not before deploying. So here is the one and only correct answer:

 

We only support Active/Passive SQL Clustering with the default instance..!!!
Does this mean we dont support named instances at all?

Yes, you thought right we dont!

Do I like this?

No I dont!!!!!