This is just a quick note to point out the example on the Railo Blog on their cluster scope:

Railo Blog: Cluster Scope

Read the blog entry for details, but basically it boils down to server A registering server B and vice versa. After which you can then use Cluster as a scope on either machine. Set cluster.x to 1 on machine A and machine B can read it. What's impressive is that you can also use the admin to determine if the updates have failed.