[RndTbl] strange NTP problem on one of 3 peers

[Kevin McGregor]

If one NTP server in your list is significantly off, the NTP algorithm
should notice and eliminate it from its calculations automatically. I
wouldn't worry about that point. None of these are virtual, are they?

On Wed, Apr 25, 2012 at 11:56 AM, Gilles Detillieux <
grdetil at scrc.umanitoba.ca> wrote:

> On 04/25/2012 11:03 AM, Gilbert E. Detillieux wrote:
>
>> Are you sure ntpd is running on all systems? Try running the following
>> command, on each of your systems:
>>
>> /usr/sbin/ntpq -p
>>
>> This will tell you not only whether ntpd is running, but also where each
>> one is getting its clock settings from, what the drift is, etc.
>>
>> Note that if the initial clock setting is too far out of whack, ntpd may
>> not even start properly. It's usually useful to run ntpdate first, to at
>> least start off with a close-to-synchronized clock. For some reason,
>> RHEL systems don't do that by default even when you enable ntpd.
>>
>
> I ran that on all 3 systems, and it shows ntpd is indeed running on all.
>  SL 5 does seem to run ntpdate first, before starting ntpd, to get the
> clock sync'ed up beforehand, as long as you have systems defined in
> /etc/ntp/step-tickers or you put a -x in OPTIONS in /etc/sysconfig/ntpd.
>
> But I wonder if there are some NTP servers on the net that are out of
> whack.  When I run ntpq, the system that has the drift (cliff) shows
> different results than the other two:
>
> On cliff:
>     remote           refid      st t when poll reach   delay   offset
>  jitter
> ==============================**==============================**
> ==================
>  caustique.anox. 209.51.161.238   2 u    5   64   73   35.302   32.315
> 4564.06
>  tb.mircx.com    64.90.182.55     2 u    2   64   77   46.530   72.637
> 4517.32
>  cliff.scrc.uman .INIT.          16 u    -   64    0    0.000    0.000
> 0.000
>  larry.scrc.uman 208.80.96.70     3 u   16   64   76    0.001  6019.84
> 3675.39
>  dave2.scrc.uman 209.167.68.100   3 u    4   64   42    0.001  6140.53
> 3858.45
> *LOCAL(0)        .LOCL.          10 l    2   64   77    0.000    0.000
>  0.001
>
> On larry:
>     remote           refid      st t when poll reach   delay   offset
>  jitter
> ==============================**==============================**
> ==================
> +zeus.yocum.org  131.188.3.220    2 u  148  256  377   35.330   -2.723
>  3.170
> *ellen.linuxgene 142.3.100.2      2 u  214  256  377   31.665   -1.240
>  2.296
>  cliff.scrc.uman .INIT.          16 u   17   64    0   27.461  -87882.
> 0.000
>  larry.scrc.uman .INIT.          16 u    - 1024    0    0.000    0.000
> 0.000
> +dave2.scrc.uman 209.167.68.100   3 u  204  256  377    0.400    2.594
>  0.890
>  LOCAL(0)        .LOCL.          10 l   44   64  377    0.000    0.000
> 0.001
>
> dave2's results are similar to larry's.
>
> A few other things I thought I should point out:  All 3 systems have ports
> 123/tcp and 123/udp open in iptables.  The clock on cliff seems to drift
> whether or not ntpd is running, though that could be because the calculated
> drift compensation is out of whack.  The /var/lib/ntp/drift file on cliff
> hasn't been modified since 1:58 this morning, before the reboot, while it
> has been on the other 2 systems.  All 3 systems have an identical
> configuration, using 0.pool.ntp.org as the step-ticker, and 0.pool.ntp.organd
> 1.pool.ntp.org as stratum 1 servers.
>
>
> --
> Gilles R. Detillieux              E-mail: <grdetil at scrc.umanitoba.ca>
> Spinal Cord Research Centre       WWW:    http://www.scrc.umanitoba.ca/
> Dept. Physiology, U. of Manitoba  Winnipeg, MB  R3E 0J9  (Canada)
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