Today wiki.rubyonrails.org was briefly down, for like 30 minutes or so.
I thought it might be a problem in Phusion Passenger, seeing that the wiki is running on it. I wanted to the restart Apache, but I decided to look in the wiki log files before doing that.
It turned out the server ran out of disk space. I truncated the Apache log files, which were consuming 40 GB or so. After that, everything went back to normal.
by Genís