I'm pretty new to SQL 2005 and was wondering why would I choose to use various named instances for my different applications vs using the default instance with multiple databases? I understand that you can configure each instance as if it was a separate installation in terms of different authentication types, etc. I'm building a cluster right now and am trying to decide if I should do named instances for my various databases. Or am I way off on why I'd want to use them? Clustering the instances complicates things from what I'm reading. Each instance needs its own LUN on the SAN? Except for the quorum drive? Any help and direction on clearing this up would be greatly appreciated!!