SPVirtualPathProvider

Further strenghtening our understanding of Ghosting and Unghosting concept posted here - http://sharepointbunker.blogspot.com/2011/02/understanding-site-definitions.html

As already mentioned, Ghosting helpes in maintaining only one version of all uncustomized pages.  For example, every site has a Default.aspx that is not replicated.  Hence saving space and maintains a leaner server.  Imagine the state of the server if every site in the web application had an individual copy of Deafult.aspx saved on the server!!!

So what happens is that the common template of Default.aspx is loaded on to the memory and every site that has an uncustomized version of Default.aspx references to that.

But what happens when a page is customized!!  That cannot be maintained as a common template for all to reference to!!  This is where Unghosting and SPVirtualPathProvider comes in to picture.  The customized page gets unghosted.  It then gets saved to the content database.  And then a virtual path is provided pointing to page in the content database.