I have another vB forum which sees quite a bit more traffic, with 5 times as many users and 2 times as many posts and about 50% more monthly page views, but with only a fairly "typical" number of forums (say, 10-15) ... which runs very smoothly with very little load on the server by comparison - so I know that first forum is struggling given the traffic.
vBulletin loads details of all forums into memory with every page load - so having more than 1,000 of them is not really a good idea and (amongst other things), is where I suspect a lot of the load (and memory usage) is coming from.
I'm yet to come up with a more elegant way of managing the volume of posts and threads on this site without having so many forums (essentially, each forum represents a zoo from around the world, and there are hundreds, sometimes thousands, of threads in each forum - each one discussing a photo taken at one of those zoos - at one point we had over 120,000 photos on the site).
I own several XenForo licenses and do intend to migrate several of my sites across, but I haven't had time to spend getting to know the code yet and understanding how it all hangs together.
I'm wondering if anyone has done any testing with large numbers of forums on a XenForo site, or if anyone has enough knowledge of the way XenForo is architected to predict how it might react if we tried creating such a large number of forums?
I'm trying to work out a migration strategy - I either try migrating to XenForo first and then fix the unknown problems I might come across (hence this post - I don't know enough to predict problems yet!) ... or I try re-architecting on vBulletin first before migrating if we know XenForo is likely to struggle on my setup as it is now.