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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.

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What makes you believe it's an issue with your server, and not merely your marketing efforts not bearing fruit? –  Michael Hampton Sep 9 '12 at 21:23
    
@MichaelHampton - its because user count has gone down suddenly. And as i mentioned, posting on Facebook page isn't giving as much users as before. –  Shashank Jain Sep 10 '12 at 4:36
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That doesn't sound like an issue with your server. That sounds like your marketing efforts are less successful today than in the past. –  Michael Hampton Sep 10 '12 at 4:38
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1 Answer

A few quick things to check, assuming this isn't simply reduced interest in your site...

  • Do you have any monitoring on this system?

This is important because you would have some means of correlating user traffic/activity with system events. What if your historical graphs showed that a runaway process was pegging a CPU at 100% and causing response or availability issues for users attempting to reach your site?

  • What's the historical system /CPU load?

If you don't have this information, it would be difficult to determine what your normal system metrics look like. Perhaps your host may have some insight.

  • What is in your logs during the periods where you were unable to SSH in?

The SSH daemon being unresponsive or unavailable is a big problem. What if your system is being attacked with a denial-of-service?

  • Have you rebooted recently? :) It's worth a try.
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CPU load is very less, its around 0.5 or 0.7. I have rebooted the server, but still no luck. Which logs should I look into? Apachelog isn't of much help –  Shashank Jain Sep 10 '12 at 4:34
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