I am not sure how many people will dislike this question, and how many negative votes. But still I couldn't anywhere else to get help.
The problem is that I have seen sudden dip on the number of users on my server. And I cannot understand why this could have happened. The scripts haven't changes, and the server is of very high end configuration.
Normally server used to get over 150 users per minute. Number of users online were almost 1500 at a moment. But now, count has dipped to about 40, and online to about 600. I have a Facebook page with half a million fans. When I used to post a link to my site on the page, user count would increase to nearly 200-250. But, it doesn't do beyond 100 now.
I don't know where to look for reason, I cannot think of anything.
Server runs CentOS, has cPanel installed. It has dual E5 Romley processors and 16GB RAM.
One think I would link to point out: Today there was some strange behavior on server. I wans't able to login to it through SSH or WHM. But then, later in afternoon I was able to do so. Then again same problem in evening which resolved in evening.
I have checked DNS propogation, and the site resolved to correct IP.
What else detail should I include? Please help me on this.