I was asked the other week how to load balance the UM role, I am going to use this post to provide some simple advice to get you started.
In short, add multiple UM role servers to each Dial Plan you wish to make more resilient to application or operating system failure.
Depending on your IP Gateway you should be able to round robin or balance the load between UM servers. To remove a server temporarily you could use:
set-umserver -identity e14um01 -status nonewcalls
Simple and to the point I hope.