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We are currently running into an issue on a RHEL 5.6 server. The server randomly becomes unstable, kernel wait messages are showing up in /var/log/messages, and we've now had it reboot twice. We've sent all of our available information to Red Hat, but to troubleshoot further they have stated that they need kdump and kexec set up which includes the following:

  1. Enable the kdump service in chkconfig
  2. Set hung_task_panic to 1 in /etc/sysctl.conf
  3. Add crashkernel=128M to grub.conf to set up a memory resident monitor for kernel dumping

My big concern is the memory resident aspect of this. Has anyone else enabled kernel core dumping before? Was there any major performance impact from the memory resident? I'm just looking for feedback on others experiences.

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The times I've set up kdump, I haven't seen any performance impact. I have however seen the system stop panicing, much to my disgust. Hopefully your panic doesn't go away, and you can actually get to the root cause!

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There's no penalty for running kdump, but you shouldn't have to do this.

If your system is unstable, I'd be curious if you've tried any other troubleshooting methods? You've talked a lot about HP ProLiant gear in the past. Does the hardware in question have an IML log or does it give any indication of issues in its ILO (or DRAC, IPMI, etc.)?

Given that you're on RHEL 5.6 and 5.9 is the current edition, there's a high likelihood that you're running into a bug or bad interaction with the hardware.

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Was there any major performance impact from the memory resident?

There should not be any performance impact.

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