silvertip257 at gmail.com
Thu Jan 3 04:17:51 UTC 2013
On Wed, Jan 2, 2013 at 7:27 PM, James B. Byrne <byrnejb at harte-lyne.ca>wrote:
> > @James: Can you specifically cite why you manually power down each
> > node? Have you tried tweaking your libvirt settings in the config
> > file I noted in my earlier response to Robert?
> Two reasons. First, I am minimally familiar with kvm. The niceties of
> the options for it is beyond my kin for the nonce. Second, libvirt
> does not always work. I have had guests refuse to either suspend or
> shutdown from an automatic request to do so. When shutdown is done
> manually one discovers right away that there is a problem and which
> guest is causing it.
I hear ya. I've never had libvirt not work, but I've had an issue or two
with VMs shortly after they were created (not production at that point).
> > Set up a central NTP server and have your hosts (and not just VMs)
> > connect to it. It could be the VM host, but doesn't need to be.
> > Distribute the load to your NTP server and off of the public NTP pool
> > by running an NTP server for your servers to poll  ... it's a good
> > practice and everybody is happy.
> I do that as well. However, I run one on each host just to serve its
> own guests and configure the host to run off our central ntp server.
> >> 4. On each guest have a cron job that checks for ntpd at regular
> >> intervals which reports failures and restarts the time service as
> >> necessary. We use:
> >> JOBNAME="Check ntpd status and restart if required" ; \
> >> ntpstat > /dev/null && \
> >> if [[ $? -gt 0 ]]; then /sbin/service ntpd start; fi
> > Why not configure the ntpd daemon and stick with that?
> > It does update on its own . And ntpstat prints out the interval,
> > which matches the one mentioned at .
> > I don't believe the ntpstat script/job is necessary (I've never had to
> > do more than set ntpd to run after configuring the servers it should
> > poll).
> You misunderstand the purpose of the job. Netstat checks to see if
> the daemon is actually running. If it is not then netstat returns a
> non-zero exit code. If the ntpstat exit code is not zero then the
> service script is invoked to restart it. Additionally, netstat writes
> out to stderr that it could not find the daemon which gets emailed to
> support. I probably should have used [[ ! $? -eq 0 ]] but what I have
> written does work.
> We found ntpd just stoped on some guests upon occasion without any
> visible trace of a cause. Not frequently but when it did happen it
> was a nuisance to detect before clock drift on the guest caused some
> failure or other. This job detects these occurrences and self
I'll have to check my hosts tomorrow and see if there's any drift.
Thanks for the explanation.
> These are all CentOS-6.3 hosts and guests.
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> James B. Byrne mailto:ByrneJB at Harte-Lyne.ca
> Harte & Lyne Limited http://www.harte-lyne.ca
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// SilverTip257 //
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