I've been looking at some .net blogs (like community server, subtext , etc...) and I noticed that the  permanent  link  for  blog post are structured such as  archive/2006/09/14/[blog title].aspx or  somewhat similar  to that.

My question is, for each posted blog, is an actual .aspx page being created and stored in that directory or is that url being created dynamically or something. Because I just don't see the point to store each blog on the server.  If each blog is actually being stored that means if you have 2000 blogs, you will have 2000 aspx files, which just seems a little much to me. Can someone please enlighten me...thanks

That is usually done by rewriting the url and not by storing individual pages. There are many articles you could find w/google describing how to do it.

for example: http://www.aspnetworld.com/articles/2004011901.aspx