AW: AW: [chrony-users] chronyd: Can' Synchronize WHY ?

[<thomas.schmid@xxxxxxxxx>]

Hi Bill,
>Overlap
>A says that the time offset is 3ms plus or minus 1 ms. Ie, it says the time is
>between 2 and 4 ms out. B saus that the offset is -6ms plus or minus 2 ms, ie
>from -8 to -4 ms out. Which of the two is the system to use?
>
>Is the clock between -8 and -4ms out or is it between 2 and 4 ms out?
>The two bands do not overlap. They are incompatible and chrony cannot decide.
To the point, thanks. I also read the article in about the "selection" mechanism in
"http://www.eecis.udel.edu/~mills/ntp/html/select.html"; quoted by Miroslav, which
(for NTP) was surprisingly easy to comprehend. I tend to treat NTP and its mechanisms
as a black box: "Believe it, it works, smart people have devised it". But of course
if the operating conditions change, this might no longer be true..

I am still trying to find out on why I have 3 (normally reliable) time sources which
deviate from each other in such a way, that no solution to whom might be right can 
be drawn by chronyd.

On Fri, 9 Sep 2011, thomas.schmid@xxxxxxxxx wrote:

> Hi Miroslav,
>> -----Ursprüngliche Nachricht-----
>> Von: Listengine [mailto:listengine@xxxxxxxxxxxxxxxxx] Im Auftrag von
>> Miroslav Lichvar
>> Gesendet: Donnerstag, 8. September 2011 10:58
>> An: chrony-users@xxxxxxxxxxxxxxxxxxxx
>> Betreff: Re: [chrony-users] chronyd: Can' Synchronize WHY ?
>>
>> On Thu, Sep 08, 2011 at 06:35:34AM +0000, thomas.schmid@xxxxxxxxx
>> wrote:
>>>>> ^x <WAN-IP1>                        1    6     49    +13us[ -
>> 877us]
>>>> +/- 1148us
>>>>> ^x <WAN-IP2>                        2    6     46   +192ms[
>> +192ms]
>>>> +/-   56ms
>>>>
>>>> Yee gads, that's pretty horrible, except for wanIP1
>>>> IP2 seems really really far away. Why is it taking so long?
>>> <WAN-IP1> is connected by a 7 Mbps WAN connection, 2 LAN and 1 WAN-
>> hop away.
>>> <WAN-IP2>: The intermediate NTP server (WinXP+Meinberg ntpd) sits in
>> the same
>>> LAN; however the WinXP is a virtual machine running on VMware Server
>> 1.0.10.
>>> Note: I know it's a big NO NO to run NTP servers out of (VMware)
>> virtual machines,
>>
>> The intervals for the two sources don't overlap, and there is no third
>> source which would overlap one of the two, so chrony gives up on them.
> Would you be so kind as to give me a "Dummie's Guid to "Overlap" ? I do
> not understand much of the values presented (dropped out of too math class
> too early :-)
>
>
>>
>> If you want to keep the WAN-IP2 source as a backup, you can try to
>> increase its stratum by the minstratum option.
>>
>>>>> ^x SU-Server1.<domain>       0    7    10y     +0ns[   +0ns] +/-
>>>> 0ns
>>>>> ^x LU-Server.<domain>         0    7    10y     +0ns[   +0ns] +/-
>>>> 0ns
>>>>
>>>> Well something is certainly screwed up there. This says that the
>> last
>>>> measurement was 10 years ago. Also while this says it is 0 ns
>> jitter,
>>>> below it
>>>> says it is 4000ms jitter.
>>>> Something is seriously messed up here
>>
>> These are just the default values when no samples were collected yet.
>>
>>>> You only have two servers, the WAN servers, and they disagree on
>> what
>>>> the
>>>> right time is. Chrony has no idea which one to believe, since there
>> are
>>>> only
>>>> two of them (whichis why you should have an odd number.)
>>> Hm, even if I have 3 valid NTP servers (setup with a valid <WAN-IP1>,
>>> <WAN-IP2> and "SU-Server3") I see the "can't synchronize" message a
>> lot.
>>
>> Is stratum for the third server 3 or higher? The sources output might
>> help.
> I tested the 3 reference setup on another system: There are some "can't
> synchronize" messages, less than the original 2 reference server setup,
> but still a few:
>
> Setup (chrony_server.conf, included into chrony.conf):
>  server <WAN-IP1> iburst prefer presend 5
>  server su-server3 maxpoll 7
>  server <WAN-IP2> presend 5
>  server su-server1 maxpoll 7
>  server lu-server maxpoll 7
>  initstepslew 30 <WAN-IP1> <WAN-IP2>
> Again, su-server1 and lu-serevr are not reachable
>
> syslog:
> ...
> Sep  8 23:07:56 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:08:12 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:11:26 Com-PC chronyd[3237]: Can't synchronise: no majority
> Sep  8 23:12:08 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:13:40 Com-PC chronyd[3237]: Selected source <WAN-IP2>
> Sep  8 23:14:26 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:18:15 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:18:59 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:19:00 Com-PC chronyd[3237]: Can't synchronise: no majority
> Sep  8 23:19:24 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:20:09 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:22:27 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:23:59 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:24:45 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:30:53 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:32:45 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:34:16 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:35:12 Com-PC chronyd[3237]: Can't synchronise: no majority
> Sep  8 23:35:24 Com-PC chronyd[3237]: Selected source <WAN-IP2>
> Sep  8 23:36:11 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:37:42 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:39:36 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:41:08 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:41:53 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:43:02 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:44:11 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:45:57 Com-PC chronyd[3237]: Can't synchronise: no majority
> Sep  8 23:46:27 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> Sep  8 23:49:11 Com-PC chronyd[3237]: Selected source SU-Server3
> Sep  8 23:49:54 Com-PC chronyd[3237]: Selected source <WAN-IP1>
> ...
>
> chronyc:
> chronyc> sources
> 210 Number of sources = 5
> MS Name/IP address        Stratum Poll LastRx Last sample
> ============================================================================
> ^* <WAN-IP1>                 1    6     67    -36us[ -463ms] +/-   85ms
> ^+ SU-Server3                2    6     42   +394ms[ +394ms] +/-  133ms
> ^+ <WAN-IP2>                 2    6     35    +83ms[  +83ms] +/-   47ms
> ^? SU-Server1                0    7    10y     +0ns[   +0ns] +/-    0ns
> ^? LU-Server                 0    7    10y     +0ns[   +0ns] +/-    0ns
> chronyc> sourcestats
> 210 Number of sources = 5
> Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
> ==============================================================================
> <WAN-IP1>                  7   5   412  -1555.346   3022.979  -9053us  2933us
> SU-Server3                 4   4   193  -2718.528  18920.604   +323ms   873us
> <WAN-IP2>                  5   4   342  -2080.739   9921.691    +56ms  5675us
> SU-Server1                 0   0     0      0.000   2000.000     +0ns  4000ms
> LU-Server                  0   0     0      0.000   2000.000     +0ns  4000ms
>
> I have attached the (I think) relevant log files as well as the
> sources/sourcestats/tracking output of chronyc.
>
> Regs,
> Thomas Schmid
>

--
William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
UBC, Vancouver,BC  |   Program in Cosmology |     unruh@xxxxxxxxxxxxxx
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