Dear rcschaff,
Thanks for your explanation. At my "top" command there is no high process. But it suddenly get higher and higher then it down. I have the CSF log when it get more than 10% load. But nothing CPU and or Memory consume high resources. Only amavis consume 16% of memory, but it is ok. I have 8Gb Memory. That is why I really confuse.
When it started get higher more than 5%, I run this command to show the highest cpu and memory usage:
ps -eo user,pid,ppid,cmd,%mem,%cpu --sort=-%mem | head
But from the result there is nothing. CPU load just average 0.xx% and Memory too, just amavis consume 16%, but I'm sure it wont cause server down.
Ater that, the load get higher and higher so quickly, and vps down. I can access the vps through VNC and I can see it did not down, because the uptime still continuing.
Is it possible CSF Firewall cause high load without able to be monitored?
I use vps KVM from contabo.com. May be you or someone else know about this company.