On Wed, Jan 2, 2013 at 7:27 PM, James B. Byrne byrnejb@harte-lyne.cawrote:
@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 [0] ... 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.
- 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 [1]. And ntpstat prints out the interval, which matches the one mentioned at [1]. 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 corrects.
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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