From October 2001 but still quite relevant, is a document on MSDN which is part of the Cold Rooster application where they worked out their decision to use SQL Server instead of the hard drive for file storage.
"Summary: Summarizes the study that was used to measure the performance difference between a database and a file system. It also explores the data modeling used to design the objects that support the ColdStorage sample Web Service hierarchical storage and infrastructure. (11 printed pages)"
It is a VERY useful "best practices" doc which I often point people to.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncold/html/storagedbdsgn.asp