The default WEBrick server that runs when you launch Instiki is OK for light loads. For a more heavily-trafficked wiki, you might want to switch to Mongrel. Fortunately, this is extremely easy.
If you don’t already have Mongrel, install it,
% gem install mongrel
For Ruby 1.9.2, you need
% gem install mongrel --version '>=1.2pre'
Then, just type
% ./instiki --daemon
Instiki will start up using Mongrel instead of WEBrick.
See the general instructions for launching Instiki at startup. The same startup script should work, unmodified, with Mongrel.
As with WEBrick, you can proxy your Mongrel instance behind a conventional webserver, like Apache. For yet higher performance, you want to have multiple back-end processes to handle multiple simultaneous requests from the front-end webserver.
Nowadays, I think, the preferred technique for getting multiple back-end Instiki processes, running behind an Apache webserver, is to use Passenger.
Other options, for getting multiple Mongrel instances, include
mongrel_cluster and Apache’s
mod_proxy_balancer. But now you’ve plumbed the depths of my knowledge, so someone who’s actually used one of these will have to fill in the details.