[chrony-users] Sporadic NTP dropouts (bad maximum delay ratio and maximum delay dev ratio)

[Ulrich Schwesinger <ulrich.schwesinger@xxxxxxxxxxxx>]

Hi,

I'm using chrony in client mode hooked up to a local NTP server. I get sporadic occurrences where NTP synch fails. I'm a bit unsure how to interpret the measurements.log file, and would appreciate any help.

========================================================================================================================
   Date (UTC) Time     IP Address   L St 1234 abc 5678 LP RP Score Offset     Peer del. Peer disp. Root del.  Root disp.
========================================================================================================================
2015-05-20 15:47:57 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.276e+00  6.211e-04  2.350e-06  0.000e+00  7.948e+00
2015-05-20 15:47:59 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.276e+00  6.910e-04  2.432e-06  0.000e+00  7.948e+00
2015-05-20 15:48:01 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.276e+00  7.341e-04  2.520e-06  0.000e+00  7.947e+00
2015-05-20 15:48:01 192.168.0.30    N 13 1111 111 1111  5  5 0.00  1.440e-04  6.550e-04  2.346e-06  0.000e+00  7.948e+00
2015-05-20 15:48:35 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.125e-03  7.180e-04  3.838e-05  0.000e+00  7.948e+00
2015-05-20 15:49:08 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.167e-03  6.460e-04  1.070e-06  0.000e+00  7.948e+00
2015-05-20 15:49:40 192.168.0.30    N 13 1111 111 1111  5  5 0.03 -2.067e-03  7.120e-04  1.083e-06  0.000e+00  3.948e+00
2015-05-20 15:50:13 192.168.0.30    N 13 1111 111 1111  5  5 0.08 -2.950e-04  6.780e-04  1.056e-06  0.000e+00  3.948e+00
2015-05-20 15:50:45 192.168.0.30    N 13 1111 111 1111  5  5 0.17 -4.600e-05  6.540e-04  1.012e-06  0.000e+00  1.948e+00
2015-05-20 15:51:17 192.168.0.30    N 13 1111 111 1111  5  5 0.28 -1.600e-05  7.250e-04  1.242e-06  0.000e+00  1.949e+00
2015-05-20 15:51:49 192.168.0.30    N 13 1111 111 1111  5  5 0.42 -4.100e-05  6.750e-04  1.135e-06  0.000e+00  9.483e-01
2015-05-20 15:52:22 192.168.0.30    N 13 1111 111 1111  5  5 0.58 -3.700e-05  7.160e-04  1.187e-06  0.000e+00  9.488e-01
2015-05-20 15:52:54 192.168.0.30    N 13 1111 111 1111  5  5 0.78 -4.300e-05  6.640e-04  1.149e-06  0.000e+00  4.485e-01
2015-05-20 15:53:26 192.168.0.30    N 13 1111 111 1111  5  5 0.83 -1.600e-05  7.360e-04  1.166e-06  0.000e+00  4.490e-01
2015-05-20 15:53:59 192.168.0.30    N 13 1111 111 1111  5  5 0.92  1.370e-04  9.150e-04  1.000e-06  0.000e+00  1.986e-01
2015-05-20 15:54:31 192.168.0.30    N 13 1111 111 1111  6  5 0.03  6.100e-05  7.540e-04  1.045e-06  0.000e+00  1.991e-01
2015-05-20 15:55:36 192.168.0.30    N 13 1111 110 1111  6  6 0.13  2.700e-04  1.270e-03  1.001e-06  0.000e+00  7.411e-02
2015-05-20 15:56:41 192.168.0.30    N 13 1111 111 1111  6  6 0.27 -3.700e-05  6.530e-04  1.000e-06  0.000e+00  1.166e-02
2015-05-20 15:57:45 192.168.0.30    N 13 1111 111 1111  6  6 0.43  8.000e-06  7.440e-04  1.032e-06  0.000e+00  1.167e-02
2015-05-20 15:58:50 192.168.0.30    N 13 1111 111 1111  6  6 0.63 -8.000e-06  6.920e-04  1.002e-06  0.000e+00  1.167e-02
2015-05-20 15:59:55 192.168.0.30    N 13 1111 111 1111  6  6 0.85 -1.600e-05  6.810e-04  1.010e-06  0.000e+00  1.169e-02
2015-05-20 16:01:00 192.168.0.30    N 13 1111 111 1111  7  6 0.10  0.000e+00  7.280e-04  1.030e-06  0.000e+00  1.170e-02
2015-05-20 16:03:58 192.168.0.30    N 13 1111 111 1111  7  7 0.38  9.200e-05  7.360e-04  1.001e-06  0.000e+00  1.149e-02
========================================================================================================================
   Date (UTC) Time     IP Address   L St 1234 abc 5678 LP RP Score Offset     Peer del. Peer disp. Root del.  Root disp.
========================================================================================================================
2015-05-20 16:05:53 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -1.912e+00  6.830e-04  2.408e-06  0.000e+00  7.948e+00
2015-05-20 16:05:55 192.168.0.30    ? 16 1111 111 1001  5  5 0.00 -1.912e+00  6.451e-04  2.350e-06  0.000e+00  0.000e+00
2015-05-20 16:06:03 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -1.911e+00  7.000e-04  2.440e-06  0.000e+00  7.948e+00
2015-05-20 16:06:05 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -1.910e+00  7.020e-04  2.444e-06  0.000e+00  7.948e+00
2015-05-20 16:06:06 192.168.0.30    N 13 1111 111 1111  5  5 0.00  8.800e-05  6.810e-04  1.213e-06  0.000e+00  7.948e+00
2015-05-20 16:06:40 192.168.0.30    N 13 1111 111 1111  5  5 0.00  6.510e-03  6.770e-04  3.067e-06  0.000e+00  7.948e+00
2015-05-20 16:07:12 192.168.0.30    N 13 1111 111 1111  5  5 0.00  5.663e-03  6.870e-04  1.248e-06  0.000e+00  3.948e+00
2015-05-20 16:07:45 192.168.0.30    N 13 1111 111 1111  5  5 0.03  5.359e-03  6.800e-04  1.157e-06  0.000e+00  3.948e+00
2015-05-20 16:08:18 192.168.0.30    N 13 1111 111 1111  5  5 0.08 -1.900e-05  6.920e-04  1.140e-06  0.000e+00  1.948e+00
2015-05-20 16:08:50 192.168.0.30    N 13 1111 111 1111  5  5 0.17 -5.200e-05  6.860e-04  1.028e-06  0.000e+00  1.949e+00
2015-05-20 16:09:23 192.168.0.30    N 13 1111 111 1111  5  5 0.28 -4.700e-05  7.220e-04  1.211e-06  0.000e+00  9.484e-01
2015-05-20 16:09:55 192.168.0.30    N 13 1111 111 1111  5  5 0.42 -5.400e-05  6.470e-04  1.222e-06  0.000e+00  9.489e-01
2015-05-20 16:10:27 192.168.0.30    N 13 1111 111 1111  5  5 0.58 -5.600e-05  6.790e-04  1.256e-06  0.000e+00  4.485e-01

I marked some lines that look suspicious to me. In in the first line, some test seems to fail [110]. In the 2nd line, suddenly the offset jumps up to -1.9 seconds.
For the 3rd line, from the documentation I found this:

Leap status: ? means the remote computer is not currently synchronised.
5678: Tests for maximum delay, maximum delay ratio and maximum delay dev ratio, against defined parameters, and a test for synchronisation loop (1=pass, 0=fail) [1111]

So that would mean that delay ratio and delay dev ratio is bad...not sure what that really means though.


I find this very hard to debug, is there any other thing I could do to find out what's exactly going wrong?

Thanks for your answers in advance,

Ulrich