On Mon, 09 Dec 2013 12:13:22 -0600 Chris J Arges <[email protected]> wrote:
> On 12/09/2013 11:50 AM, Serge Hallyn wrote: > > Chris Arges (cc:d) has looked into this before in-depth. But I > > don't seem to have the email with his conclusions. Chris, could > > you summarize here what you had found when you looked into our > > previous suggestion to not enable ntp in guests? > > > > Hi, > > Here is the original thread about this topic: > https://lists.ubuntu.com/archives/ubuntu-server/2013-April/006556.html > > Originally we had recommended _not_ to use NTP on VMs, but after > researching this a bit further it seemed clear that NTP should work > perfectly fine. The modification I made is updated here: > https://help.ubuntu.com/community/KVM/FAQ#Should_ntp_be_used_for_time_synchronisation.3F > > My statement was pretty vague on purpose. > If you are doing lightweight stuff when you boot the VM the kvmclock > will setup the clocksource just fine and we expect the system time to > not drift too much while the VM is up. > For heavy duty stuff where you have many VMs, they run for a long > time , or never shutdown/reboot the machine, it makes sense to setup > NTP client on the VM using the host machine as the ntp server. I would like to point out that my original email -- and the start of this thread -- was not fixed on having NTP running on VMs in particular, but *servers* generically. So, I guess, we *should*: * be running NTP on bare-metal servers; * be running NTP on VMs, set to sync with the host. Of course, this is a simplification: on a complex environment, a single source for time sync should be selected for *all* bare-metals. Which one, if a stratum 1 or 2 (or even lower) is not a problem -- as long as all the machines are syncing to the same time provider. But, on a default install, using the *.ntp.ubuntu.com providers, we would have this, even if all the bare-metals directly sync to *.ntp.ubuntu.com (but this is would not be ideal). ..C.. -- ab alio expectes alteri quod feceris
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