Writes JustDave:
One thing to keep in mind is that I would bet that the majority of the better php forums out there, such as ubb.threads, will be using pretty much the same amount of resources (yes it will vary some but I bet as far as the cream of the crop goes they will be close). This is because they have MySQL in common. If your site is growing at that rate to where it doubles every 6 months I have to wonder if you wouldn't be better off getting Infopop's Open Topic? This would be scalable and then some as your needs grow.
Just my 2 cents. 
Yeah, but I want the features I want, I like UBBT, and I'm stubborn
!
So I've been cobbling together solutions:
1. use gzip compression
2. get a server with dual processors
3. limit people's ability to search all forums all the way back (we'll charge 'em for that, actually...THAT'LL limit 'em!)
4. PHP Accelerator (
http://www.php-accelerator.co.uk).
5. prayer
6. have backup S/W ready to install if our server crashes Mike Tyson-like under the load.
Best would be if UBBT could hook into postgres. Doesn't look like that's currently being worked on, though it's been bandied about over the years. Postgres seems to be getting very "hot" in many circles exactly because of its scaling robustness.
Also, Infopop promises to try and work up some benchmarks re: what scaling is possible with UBBT. If they don't, larger sites are going to remain terrified to install (which, in turn, will perpetuate the dearth of real world scalability data). This should be of concern to InfoPop (they're limiting their market) and to all of you. Good communities grow quickly. And UBBT communities tend to be good communities. Scaling issues are really important.
JIM
