Mailing List Archive

A short update: Interestingly the VM gained 77s (I had expected it _lost_ some time).

>>> "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> schrieb am 16.04.2014 um
09:18 in Nachricht <534E4ADD020000A10001558E@gwsmtp1.uni-regensburg.de>:
> Hello!
>
> I managed to migrate my Xen virtual machines live from one node to another.
> Soe of the VMs have several GB of RAM with databases, so live migration takes
> a while. However the typical user does not notice that the node migrated
> (network connections stay alive). Unfortunately NTP seems to notice the time
> migration took (77s in this case):
>
> ntpq -pn
> remote refid st t when poll reach delay offset
> jitter
> ============================================================================
> ==
> *127.127.1.0 .LOCL. 10 l 3 64 377 0.000 0.000
> 0.001
> 132.199.176.18 192.53.103.108 2 u 180 512 377 0.239 -77753.
> 41560.8
> 132.199.176.153 192.53.103.104 2 u 185 512 377 0.275 -77751.
> 41560.1
> 172.20.16.1 132.199.176.153 3 u 191 512 377 0.378 -77753.
> 41560.5
> 172.20.16.5 132.199.176.18 3 u 251 512 377 0.107 -77754.
> 41560.2
>
> So it thinks the other nodes are off by 77.7 seconds and sync to ist own
> clock.
>
> Other VMs show simular results:
> # ntpq -pn
> remote refid st t when poll reach delay offset
> jitter
> ============================================================================
> ==
> *127.127.1.0 .LOCL. 10 l 6 64 377 0.000 0.000
> 0.001
> 132.199.176.18 192.53.103.108 2 u 582 1024 377 0.242 -78361.
> 78359.9
> 132.199.176.153 192.53.103.104 2 u 546 1024 377 0.521 -78360.
> 78360.1
>
> # ntpq -pn
> remote refid st t when poll reach delay offset
> jitter
> ============================================================================
> ==
> *127.127.1.0 .LOCL. 10 l 64 64 377 0.000 0.000
> 0.001
> 132.199.176.18 192.53.103.108 2 u 653 1024 377 0.326 -77837.
> 77836.7
> 132.199.176.153 192.53.103.104 2 u 969 1024 377 0.453 -77835.
> 77835.8
> 172.20.16.1 132.199.176.153 3 u 971 1024 377 4.937 -77837.
> 77834.5
> 172.20.16.5 132.199.176.153 3 u 966 1024 377 6.283 -3.295
> 77836.9
>
> As it turn out, the time in the VMs is actually wrong after migration:
> # ntpq -pn
> remote refid st t when poll reach delay offset
> jitter
> ============================================================================
> ==
> 127.127.1.0 .LOCL. 10 l 51 64 377 0.000 0.000
> 0.001
> +132.199.176.18 192.53.103.108 2 u 71 1024 377 0.362 -77840.
> 2.573
> +132.199.176.153 192.53.103.104 2 u 386 1024 377 0.506 -77838.
> 2.834
> *172.20.16.1 132.199.176.153 3 u 391 1024 377 4.140 -77840.
> 2.744
> +172.20.16.5 132.199.176.18 3 u 386 1024 377 3.767 -77841.
> 1.409
>
> If I want to continue to use NTP, what are the recommendations?
>
> Regards,
> Ulrich
>
>
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