| Re: [chrony-users] Chrony offset and stability adjustments? (fwd) |
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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] Chrony offset and stability adjustments? (fwd)
- From: Bryan Christianson <bryan@xxxxxxxxxxxxx>
- Date: Tue, 8 Jan 2019 08:46:20 +1300
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> On 8/01/2019, at 7:53 AM, Bill Unruh <unruh@xxxxxxxxxxxxxx> wrote:
>
> For a few 10s of dollars you can hook up a gps/pps to your hadware and have it
> discipline the base system clock (not the VM clocks) to better than 10musec
> (and sometimes better than 1musec).
My home LAN has an rpi3 + uptronics GPS hat providing NTP service.
A linux host on the LAN runs 2 VirtualBox VMs - all 3 (host + VMs) using the rpi as their NTP server.
All the machines are using chrony
From the stats below you can see that root dispersion is < 100usecs on all the machines and that system time offset is better than 10usecs
RPI3 - raspian stretch lite (fleur)
root@fleur:~# chronyc -n tracking
Reference ID : 50505300 (PPS)
Stratum : 1
Ref time (UTC) : Mon Jan 07 19:35:38 2019
System time : 0.000000057 seconds slow of NTP time
Last offset : -0.000000075 seconds
RMS offset : 0.000000061 seconds
Frequency : 6.495 ppm fast
Residual freq : -0.000 ppm
Skew : 0.005 ppm
Root delay : 0.000000 seconds
Root dispersion : 0.000007 seconds
Update interval : 8.0 seconds
Leap status : Normal
Linux Host (cora)
root@cora:~# chronyc -n tracking
Reference ID : 112EAB25 (2600:70ff:c07f::4)
Stratum : 2
Ref time (UTC) : Mon Jan 07 19:36:50 2019
System time : 0.000000630 seconds slow of NTP time
Last offset : -0.000001557 seconds
RMS offset : 0.000002037 seconds
Frequency : 29.022 ppm fast
Residual freq : -0.003 ppm
Skew : 0.058 ppm
Root delay : 0.000294303 seconds
Root dispersion : 0.000024607 seconds
Update interval : 8.0 seconds
Leap status : Normal
root@cora:~#
Linux VM (millie64)
root@millie64:~# chronyc -n tracking
Reference ID : 0A400119 (10.64.1.25)
Stratum : 2
Ref time (UTC) : Mon Jan 07 19:38:13 2019
System time : 0.000000020 seconds slow of NTP time
Last offset : +0.000000033 seconds
RMS offset : 0.000000859 seconds
Frequency : 0.206 ppm slow
Residual freq : +0.000 ppm
Skew : 0.016 ppm
Root delay : 0.000401451 seconds
Root dispersion : 0.000028598 seconds
Update interval : 16.2 seconds
Leap status : Normal
Linux VM (plexconnect)
root@plexconnect:~# chronyc -n tracking
Reference ID : 0A400119 (10.64.1.25)
Stratum : 2
Ref time (UTC) : Mon Jan 07 19:39:25 2019
System time : 0.000000967 seconds slow of NTP time
Last offset : -0.000000509 seconds
RMS offset : 0.000001911 seconds
Frequency : 0.186 ppm slow
Residual freq : -0.001 ppm
Skew : 0.046 ppm
Root delay : 0.000415433 seconds
Root dispersion : 0.000025371 seconds
Update interval : 8.1 seconds
Leap status : Normal
Bryan Christianson
bryan@xxxxxxxxxxxxx
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