[CentOS] Server hangs on CentOS 5.5

Tue Mar 8 17:50:30 UTC 2011
Brian Mathis <brian.mathis at gmail.com>

On Tue, Mar 8, 2011 at 12:24 PM, Michael Eager <eager at eagerm.com> wrote:
> Hi --
> I'm running a server which is usually stable, but every
> once in a while it hangs.  The server is used as a file
> store using NFS and to run VMware machines.
> I don't see anything in /var/log/messages or elsewhere
> to indicate any problem or offer any clue why the system
> was hung.
> Any suggestions where I might look for a clue?

Please be more specific when you say it "hangs".  Does it just pause
for a minute and then continue working, or does it freeze completely
until you reboot it?  Does it respond to s "soft" reboot like
Ctrl-Alt-Del, or do you need to hard power it off?

Since this is an NFS server I'm going to guess there might be a lot of
IO.  Maybe there is some large IO load going on, like maybe all your
VMs are running anti-virus scan at the same time, or something like

To troubleshoot, I recommend installing the 'sar' utilities (yum
install sysstat) and then reviewing the collected data using the
'ksar' utility (http://sourceforge.net/projects/ksar/).  sar/ksar are
good for tracking down acute problems.