'Live' Migrate messes up NTP on FreeBSD domU - any suggestions?

[Karl Pielorz]

--On 2 November 2015 at 18:40:43 +0100 Roger Pau Monné 
<roger.pau at citrix.com> wrote:


>>     remote        refid      st t when poll reach   delay   offset jitter
>> ========================================================================
>> === ntp0      193.67.79.202    2 u  931 1024  377    0.232  -4977.5
>> 4207.29 ntp1       66.228.38.73    3 u  890 1024  377    0.267  -4988.5
>> 4616.94 ntp2      64.246.132.14    2 u  990 1024  377    0.324  -4978.0
>> 4207.98 "
>
> I'm sorry, but I have no idea about ntpd, what does the above mean? The
> offset is too big with other peers and ntpd simply disconnects?

Sorry for being so vague (I half hoped someone must have run into this 
before and posted a "Yes, we noticed the same - this fixes it" reply :)

The above seems to show that time moved forward on the VM by a few seconds. 
This doesn't always happen - I just moved another VM and that shows 'offset 
= 8000'. Yet another VM moved at the same time is fine.

Comparing the output of 'date' for that offset 8000 VM with a known 'good' 
clock - it shows the VM is indeed 8 seconds in the future after the move.

ntp is fussy - and kind of understandably decides that's too much time 
difference to slowly ebb away - so just gives up and leaves the VM clock 
'as is'.

The XenServer the VM was residing on (and the new one it's resident on) 
both on their server consoles show the correct time (i.e. neither are 8 
seconds 'ahead') - so it looks like the move somehow gained us 8 seconds 
(or 5 seconds in the original example).

> There were some issues that I fixed some time ago regarding migration
> and PVHVM guests:
>
> http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=f8e8fd56bd7d5675e8331
> b4ec74bae76c9dbf24e
> http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=32c864a35ece2c24a336d
> 183869a546798a4b241
>
> You should make sure XenServer has both of this commits.

I'll have a look at those - we might be a bit stuck for implementing them 
if they're XenServer changes, as we run the XenServer ISO's (6.5 SP1 
w/hotfixes).

-Karl