[CentOS] Strange reboots

[Linux]

On Fri, Apr 11, 2008 at 3:18 AM, Linux <linuxlist at gmail.com> wrote:
> On Fri, Apr 11, 2008 at 2:43 AM, William L. Maltby
>  <CentOS4Bill at triad.rr.com> wrote:
>  >
>  > On Fri, 2008-04-11 at 02:02 +0300, Linux wrote:
>  >  > On Fri, Apr 11, 2008 at 1:44 AM, Benjamin Karhan <simon at pop.psu.edu> wrote:
>  >  > >  ] Every 59 minutes (maybe every hour) it reboots without any logs,
>  >  > >  ] without any traces and unfortunately with breaking software raid.
>  >  > >  ] After reboot dmesg does not have any strange entries.
>  >  > >  this really only helps you if you have X11 installed/enabled to begin with...

For the records...

Thanks for your responses and here is feedback:
- ssh root login is limited to certain ip's only...
- reboot is definitely a "cold reboot" but I am not a native english speaker :)
- power surge/temporary failure is not a case, datacenter has
expensive power equipment
- nor cpu heat is a case. I placed an extra thermometer and moved
server to the frond of cold air inlet.
- lmsensors or sensors does not exists.
- I tested with/out crons before. Pretty sure no relation with crons.
- External and internal services were expected to leave some marks.
Did a cronned "ps ax" and checked processes that run before restart,
nothing suspicious.

Consequently:
I had 4 DDR ECC RAM modules each 2 GB paired in 2 different brands.
Each brand functioned well as 4GB total but when all are installed
nightmare begins.
I guess (this time a real guess) I have a problem with my RAM
settings. 8 GB may cause this problem, may be a serious page fault
etc... Without grub parameter "mem=" server boots very slowly and also
responses very slowly.

Maybe I need a new thread title "Server too slow or too unstable with
8 GB RAM" :)

Thanks...