So occasionally Lighttpd on FreeBSD-7.x+ZFS gets all upset. I -think- there's something weird going on where I hit mbuf exhaustion somehow when ZFS starts taking a long time to complete IO requests; then all socket IO fails in Lighttpd until it is restarted.
More investigation is required. Well, more statistics are needed so I can make better judgements. Well, actually, more functional backends are needed so I can take one out of production when something like this occurs, properly debug what is going on and try to fix it.