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Requirements for Creating an MS DTC Resource in a Failover Cluster

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Applies To: Windows Server 2008

Before you add a Microsoft Distributed Transaction Coordinator (MS DTC) resource to a failover cluster, review the following specific requirements for MS DTC resources.

Requirements for adding an MS DTC resource to a cluster

The following table shows the requirements that must be met before you can add an MS DTC resource to a cluster.

Requirement Determining factor

You must add an MS DTC resource to a cluster group. This group can be either an existing cluster group or a new group that you define.

If you want other cluster resources to fail over with the MS DTC resources, those resources must reside in the same folder as the MS DTC resource.

For example, if you use MS DTC with SQL Server and you want them to fail over together, you must add the MS DTC resource to the group in which SQL Server resides.

If you create a new group for the MS DTC resource, you must assign a name to that group.

No two groups in a cluster can have the same name.

An MS DTC resource has two resource dependencies: a physical disk and a network name. You must ensure that these MS DTC dependencies reside in the same group as the MS DTC resource.

Note

An IP address resource is added automatically when you add a network name resource. 

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  <p>Because multiple physical disk resources are allowed in a group, you must decide where you want the MS DTC log file to reside. </p>
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The log file must reside on a disk that is shared by all nodes in the cluster.

When you install MS DTC in a clustered environment, Windows XP and Windows Server 2003 automatically create the MS DTC log file in the %Windows%/System32/msdtc folder. The name of the log file is Msdtclog.

In some cases, other resources in the group can share the physical disk with the DTC. In other cases, you might want the MS DTC log file to have its own disk.

For example, if SQL Server requires a significant amount of disk space, you can move the MS DTC log file to a physical disk that has ample space. You can move the log file after you configure the DTC as a cluster resource.

One or more nodes in the cluster must be identified as owners of the MS DTC resource.

Which nodes in the cluster will be owners of the MS DTC resource?

Creating a cluster group for an MS DTC resource

If you want to add an MS DTC resource to a new cluster group, you can use the Cluster Administrator tool to create a group. Whether or not you create a new group for MS DTC resource depends largely on what resources are available in the cluster to the DTC. For example, if the DTC does not have to share a disk from another group, the MS DTC resource and its dependent physical disk resource can reside in a separate group.

Note

The DTC ensures that applications are able to communicate with an MS DTC resource even if the MS DTC resource is running on a separate node.

Adding MS DTC resource dependencies

A resource dependency is a resource type that the DTC requires so that it can operate successfully in a cluster. An MS DTC resource has the following two resource dependencies:

  • A physical disk resource, for example, C:

  • A network name resource, for example, Cluster1

The cluster group to which you add the MS DTC resource might not always contain the correct resource dependencies. Usually, this is because you have created a new cluster group for the MS DTC resource, which is always empty until you add resources to it.

To add resource dependencies to a new cluster group, you must move them from the group in which they currently reside. You cannot copy resources from one group to another. If two cluster resources have the same resource dependency, both cluster resources must reside in the same cluster group.

For example, if an MS DTC resource and a SQL Server resource both have the physical disk F: as a dependency, both the MS DTC resource and the SQL Server resource must reside in the same group. However, if only one of the resources has the dependency on F:—for example, the DTC—you can move the dependency resource F: from the group in which SQL Server resides to the new group that you defined for the DTC.

Choosing the location for the MS DTC log file

In a clustered environment, Windows XP and Windows Server 2003 include a shared instance of the DTC. This shared instance includes a log file that is installed automatically in a default location that all owners of the MS DTC resource can share. The default location is %/Windows%/System32/msdtc/msdtclog.

For performance reasons, you might want to move the log file. For example, if your SQL Server resource is the only resource that requires transactions, you might want the MS DTC log file to reside on the same physical disk as the SQL Server resource.

You can move the MS DTC log file after you have configured the DTC as a cluster resource.

Choosing owners for an MS DTC resource

Before you add an MS DTC resource to a cluster, you must decide which nodes in the cluster you want to designate as owners of the resource. You designate a node as an owner of an MS DTC resource when you add the resource. You use the same procedure to choose owners for an MS DTC resource that you use for assigning ownership to other cluster resources.