If you're looking to back up your server, you should use the functionality that's built into the product. As I've already said, other tools don't understand Drive Extender and may not be able to back up your data. And if you use Windows Home Server you
must use Drive Extender; it's not a feature you can turn off.
If you're looking to back a client computer up to your server, you can use other tools, but you will be giving up the storage efficiency and performance that Windows Home Server gives you.
I'm not on the WHS team, I just post a lot. :)