Hi Jeff,
there are defagmentation tools designed for WHS available on the market. But my opinion to such tools and defragmentation on the server is, that they are more a placebo than bring really benefits. Not only, that for a home server the bottleneck is the network and not the disk, performing the defragmentation will use system resources on it's own and during the action slow down the system. In single cases also other issues with defragmentation tools have been reported, which ended in reinstalling the server.
Best greetings from Germany
Olaf