I've noticed some slowdown, but I figure it was more my lame-duck connection rather than the influx of visitors...but maybe it was a combination...
It's happened a lot for me, too. Something must be buggy.
Memcached doesn't seem to be working too well. We probably have to increase the amount of memory it uses, but the filesystem cache option should make all of that irrelevant now.
The real problem is that you can only have so many connections to a MySQL server going at the same time, and the Encyclopedia and forums usually hit up the server with each page view. If we were running on a few hundred machines like Wikipedia, that wouldn't be a problem because we'd support thousands of concurrent connections that way, but because we're using cheap shared hosting and our traffic goes to the same machine as a few dozen other sites, if caching isn't working, then the Encyclopedia and Forums will eat up all the connections we're given with just a few dozen simultaneous visitors.
Therefore, nothing is "buggy," so much as the site is just starved for resources. That's the reality of cheap hosting though. Fortunately only a few people edit the Encyclopedia on a regular basis, so enabling the filesystem cache should make it so everything is pretty much fixed now, and we should be able to scale up to at least several dozen times more traffic than we're getting now. If you still notice any more problems, then make sure to mention them here.
