Solution 1:

Simply install the DFS Feature on another server and add it to the namespace using the DFS Management snap-in. This will give the namespace high-availability, though it obviously does nothing for the files that it is offering referrals to.

Note that this only works on domain-based namespaces and does not work on a standalone namespace. For details, see this: http://technet.microsoft.com/en-us/library/cc732807.aspx

Solution 2:

You just need to add another folder target to your Namespace.

This article from Microsoft gives the step-by-step:

A folder target is the Universal Naming Convention (UNC) path of a shared folder or another namespace that is associated with a folder in a namespace. Adding multiple folder targets increases the availability of the folder in the namespace.

To add a folder target by using DFS Management, use the following procedure.

  1. Click Start , point to Administrative Tools , and then click DFS Management .

  2. In the console tree, under the Namespaces node, right-click a folder, and then click Add Folder Target .

  3. Type the path to the folder target, or click Browse to locate the folder target.

  4. If the folder is replicated by using DFS Replication, you can specify whether to add the new folder target to the replication group.

http://technet.microsoft.com/en-us/library/cc732105.aspx

You now have two choices, you can leave both live or have one disabled.

If you don't replicate the content, and the content is not static, then you'll have issues if both are enabled. Users won't always get the same content. One day it will be from target A and another day (or another user) will be from target B.

You can leave one disabled and enable it only in case of failure.

You can have both disabled and change the priority (in the Advanced properties tab) such that one target is "First among targets of equal cost" and the other "Last among targets of equal cost" so that one target is used and the other will be used only in case the first one is not available - provided they are equal cost. I have had varied success with that.