Unlimited numbers of Virtual Directories and Web Sites(Kristofer Gafvert, June 29, 2005)
Now and then questions comes up if there is a limit in the numbers of websites or virtual directories you can have. The answer to this is that there is no such limit in IIS 6.0.
This however does not mean that you can create unlimited of websites on a single machine, and think that they will all work satisfying. There is a limit (everything has a limit), and in this case, the limit is in hardware. Running 10 000 websites on a single machine of course means that the hardware must be able to handle all the load. Dynamic websites will decrease the number of websites you can run on a single box, while static websites will increase this number. But it is all about the hardware, and what load you put onto the webserver.
For IIS 5.0, there is a limit of roughly 5000 sites, due to "metabase expansion constraints" .
When hosting multiple websites (IIS 6.0), consider to use host headers instead of multiple IPs. The WWW Service must manage an endpoint for every site identified by a unique IP address, which means that static IP addresses will consume memory from the non-page pool.
Applies to [?]