SQL Server 2008 Fail-over Cluster

I am using SQL Server 2008 Enterprise and I want to install SQL Server 2008 fail-over Cluster. I am wondering,

(1) do I need an active directory domain? (2) what is the minimal number of machines do I need (suppose I do not have an active directory domain or domain controller yet)?

thanks in advance, George

My experience is primarily with Server 2003 Failover Clustering so this may not be exactly correct, but speaking from what I know of 2003 and have heard about 2008 the answers to your questions are as follows:

(1) Yes you need an AD Domain, SQL Clustering requires domain accounts to be configured to run the SQL Services, these accounts must be shared between the two boxes. Additionally, SQL Clustering is configured within a Windows Cluster which also uses domain accounts for authentication.

(2) You would need at minimum 2 servers (1 cluster node, 1 Domain Controller), technically you can create the cluster while only having one node available although you don't actually receive the benefits of the cluster in this scenario. Practically speaking you would want at least 3 servers, two cluster nodes with as similar hardware as possible and 1 Domain Controller.

Yes you need an AD domain for the clustering service to validate against and you need to only have two machines but both will need to also be domain controllers.