I consistently have trouble to access http://en.wikipedia.org today, though I can slowly access http://wikipedia.org/ and http://zh.wikipedia.org/. What is the problem?

Do we have server monitors for those machines? If not, I suggest to use some third party service to monitor the server's uptime and performance, like http://www.siteuptime.com or http://www.elkmonitor.com/. I guess there are some free service provider available.

We need to insure the uptime for major server, otherwise, we are going to lose users.