Introduction

The following are the high level steps required to turn an existing 2-node File Server cluster into a 3-node multisite cluster using SteelEye DataKeeper Cluster Edition. The same steps can be applied to most cluster resource types including Hyper-V, DHCP, Generic Service, etc. However, if you are working with a SQL Server cluster the steps will be slightly different as adding a node to the cluster is done through the SQL installation process and not the Failover Cluster Manager.

These instructions assume you have at least base level knowledge of Windows Server Failover Clustering and some familiarity with SteelEye DataKeeper Cluster Edition. Also, these instructions do not address any changes which may be required to support cross subnet failover utilizing the new “OR” functionality introduced in Windows Server 2008 R2. For further information on deploying multisite clusters refer to the following resources:

• http://support.microsoft.com/kb/947048/en-us
• http://download.microsoft.com/download/8/C/2/8C21BAFE-3432-48D1-962A-F7A9DD54A2AC/Multi-Site%20Clustering%20with%20Windows%20Server%202008%20Enterprise.pptx
• http://www.microsoft.com/windowsserver2008/en/us/failover-clustering-multisite.aspx

Step 1 – Start with a traditional shared storage cluster

Step 2 – Remove any Physical Disk resources from the clustered service

Step 3 – Delete the Cluster Disk from Available Storage

Step 4 – Bring the shared volume Online on all cluster nodes

Step 5 – Verify that the volumes brought online all have the same drive letter across cluster nodes. At this time Disk Management may not display the drive letters but you should be able to verify the drive letters through Windows Explorer.

Step 6 – Change your Quorum type to node majority (if you will have an odd number of nodes) or Node and File Share Majority (if you have an even number of nodes).

Step 7 – Delete the volume resource that is in Available Storage

Step 8 – Create your mirror

Step 9 – Add the remote Node to the cluster*

* IMPORTANT NOTE
If you are using Windows Server 2008 R2 SP1 , you must not do this step through the Failover Cluster Manager GUI. Changes were made in SP1 to support symmetric storage however these changes actually make deploying multisite clusters more complicated in some circumstances. If you are using SP1 and want to add a node to a multisite cluster that is using a 3^rd party storage class resource like DataKeeper, the only way to add a node without causing the cluster disks resources to be added back into the cluster (which really causes a mess to clean up) is to use PowerShell to add the node as described here http://technet.microsoft.com/en-us/library/ee461047.aspx

Step 10 – Add the DataKeeper Volume Resource

Step 11 – Change the DataKeeper Volume Parameters to associate it with the replicated volume

Step 12 – Redefine the cluster dependencies

Step 13 – Test your new multisite cluster

Keep in mind that only a shared source or the current target of a mirror can come online; you cannot bring a shared target online if it is not the current target of the mirror. In an unexpected failure Windows will follow the preferred owners list until it finds a node that is available to come online. In a manual Online if you try to bring a node Online that is not a shared source or a current target the Online will fail and the current node will remain online. Check the DataKeeper GUI to verify which node is currently the target of the mirror.

Microsoft’s latest version of SQL, code named Denali, is currently in CTP. One of the most anticipated feature is something called HADRON. Basically, it is has been described as mirroring 2.0. The best features of HADRON as I can see compared to mirroring as it is in 2005/2008 are as follows:

• You can query the mirror (now known as a replica)
• You can have more than one replica
• Database are grouped into availability groups to ensure related databases always fail over together
• Support for replicating more than 10 databases

If you want a great preview, check out fellow MVP Brent Ozar’s post, SQL Server Denali Rocks!

From reading Brent’s post I gather Microsoft only plans to include this in the Enterprise version of SQL. That is too bad for the many customers running SQL Server Standard as traditionally there is a significant price jump to go from Standard to Enterprise. However, that is good news for the 3^rd party replication vendors out there who are providing similar functionality today on SQL 2005/2008 on Standard and Enterprise Editions.

While it is not an exact duplicate of HADRON, a multisite cluster using SteelEye DataKeeper Cluster Edition for SQL Server gives you a great solution for HA/DR without requiring shared storage. So while we wait for Denali and all the application vendors to start supporting Denali you might want to have a look at what SteelEye DataKeeper Cluster Edition can do for you today!