On Wed, Jan 2, 2013 at 3:53 AM, Robert Dinse <nanook@xxxxxxxxxx> wrote:
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Mike
// SilverTip257 //
Friday, I moved our servers to a new co-lo facility and ran into an
interesting problem with virtual machines.
I did an orderly shutdown of the CentOS 6.3 host, and it in turn suspends
all the guests. It took about an hour and a half to move and fire up the host.
By default VMs suspend when the host node is shutdown. You can change this behavior in /etc/sysconfig/libvirt-guests
By shutting down the VMs you don't have to wait for the in-memory data to be dumped to disk, nor do you have to wait for it to be copied back from disk and into memory on boot.
The guests, being suspended, were then an hour and a half behind and it
seems ntpd does not want to correct more than 1000 seconds of error so it would
not automatically adjust the clocks.
At my place of employment we noticed the same thing during maintenance, the VMs had their clocks all out of whack.
I tried the -g argument which is supposed to override the 1000 second
limit but it did not. I ended up having to manually set the clocks close
enough for ntpd to correct.
I believe we had manually correct the clocks as well on ours, but it's been months since then.
Since there is no hardware clock for the virtual machines to use when they
boot, it seems that shutdown and reboot of the virtual machines probably would
not have avoided this.
Any suggestions for addressing this particular scenerio other than having
to manually set a bunch of clocks?
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Mike
// SilverTip257 //
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