Windows 2008 Cluster Shares
If you're reasonably new to windows 2008 clusters, well we don't all get to upgrade to the newest technology when it first appears, then you might find the whole process of file shares somewhat bewildering compared to w2k3. I certainly struggled with my first w2k8 cluster to be sure.
Anyway there's a great post from Core Team here http://blogs.technet.com/b/askcore/archive/2010/08/19/working-with-file-shares-in-windows-server-2008-r2-failover-clusters.aspx
You might also want to check out Allan Hirt's excellent book on SQL 2008 clustering http://www.computermanuals.co.uk/scripts/browse.asp?ref=912646