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.

  • Not a best practice, but you can also make both nodes be domain controllers, so you can do it with just two machines.
    – mfinni
    Nov 15 '10 at 16:14

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.


SQL Server Fail-Over Clustering runs on top of Windows Server Fail-over clustering.

You do need at least one AD box and two is preferrable, though the second one can actually run as a virtualized instance. AD is required as the fail-over process advertises the new name and IP address combination. You will need to set aside an IP address and name for each fail-over service (DTC, SQL Server, etc.)

Minimum number of systems in a cluster is one, but for fail-over functionality the minimum is two systems and two instances of the service and a quorum disk.

Drives need to be shareable across systems -- Windows Fail-over Cluster Configuration will test this.

I generally install a Fail-Over instance of DTC before I install any SQL Server fail-over instance.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.