We are going to make a community board based on cities, there are expected 4000 forums in it and right now the page view is assumed to be 1 million per day
I know there is forum caching problem if there are such many number of forums if I use vbulletin. As it seems load all the forum into the forumcache on each page. With 4000 forums that would be an immense amount of data.
Welcome to WebmasterWorld, funfuntimer. That's an interesting question - sometimes, you need a lot of forums to provide the proper organization. I've got a vBulletin installs with 500+ forums, but the combination of 4K forums and a million posts for design criteria is one heck of a busy forum. If you are getting a million posts,you are probably looking at tens of millions of pageviews per day.
One approach might be to break it into a number of installations (e.g., by region). I'd spend some time hunting around big-boards.com and see if anyone else has the kind of activity and forum complexity you are designing for.
rogerd, this is the reply I get from vbulletin forum:
One of the problems is that all the forums are loaded into the forumcache on each page. With 4000 forums that would be an immense amount of data. I don't think it even matters much if they're actually displayed or not.
Regindk is probably right - most forum packages are really geared to a modest number of forums. I don't know if I've ever seen an operating board with 4K individual forums. You could always try a pilot install - stuff 4K forums into the database, and see how things load up.