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I have a dedicated server that runs CentOS 6.3. Every once in a while, in the morning from around 2:00 to 6:00 in my timezone, the server freezes - I'm not sure what happens but it seems all the running processes stop. A Java application that I made kept logs every minute and at that time discontinue. I was able to connect with KVM and found a black screen, from the KVM interface I was able to restart it.

I'm wondering if anyone has any idea on how to investigate the cause of this issue. I'm not really sure what logs to look through and what I would possibly find.

Here's a picture of the bandwidth use:

As you can see, it appears to completely cut out and return when I am able to turn it back on.

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up vote 2 down vote accepted

There are few options:

  • crash of the virtualization software / KVM
  • crash of the guest OS or network stack [if your Java cron job runs locally and does not depend on the network connection we can rule out the network stack]
  • system is overloaded in some way - swaps to death, is CPU starved, hits limits on the number of processes, or runs out of memory.

To rule out running out of resources, use something like Sar or Munin and try collecting basic statistics every minute or so. Munin will give you plenty of useful stats out of the box including load average, number of processes, CPU usage, free memory, swap usage and swapping activity.

I'm worried it's a guest kernel crash or misbehavior of KVM. If so, the methods above will not help.

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The CPU and memory is always quite low so I believe I can rule that out. Perhaps I should contact the dedicated server provider about the issue. – Keenan Thompson Jan 6 '13 at 15:53
ask them to run memtest for a few hours. – pQd Jan 6 '13 at 17:43

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