I'm currently in an early design stage for a large scale web application which will definitely be hosted on a large farm of web servers. Now, I'm trying to decide whether I want the whole site to be a www.site.com and place sub-apps in folders, like www.site.com/blogs, www.site.com/messages, etc. or whether I want to have them as subdomains, e.g. blogs.site.com, messages.site.com etc. The biggest con against subdomains is that I'll be heavily using ajax and it does't like cross-domain calls, e.g. I won't be able to call a web service hosted on www.site.com from a page hosted on blogs.site.com - browser will throw a permissions exception. The biggest con against having everything under www.site.com is that I don't see a way to dedicate web farms to specific sub-apps then. Like if I want a farm to be dedicated to blogs app, then it's easy in case of using subdomains, but how do I do that if everything is under www?
I am probably lacking some knowledge on the networking part of web farm setup so any comments/ideas would be welcomed and highly appreciated!
Environment is Windows 2008 and ASP.NET 3.5