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  • Re: Re: NTP discarding servers when we have more than 3 servers configu

    From rcheaito via questions Mailing List@21:1/5 to All on Mon Feb 17 01:28:00 2025
    To: questions@lists.ntp.org

    Thanks @pessimus192 for your reply. Just for own clarification, do I need to increase minclock to 6 or maxclock to 6?
    On my system, minclock = 3 and maxclock is 10.

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  • From rcheaito via questions Mailing List@21:1/5 to All on Mon Feb 17 21:08:00 2025
    Hi Harlan,

    You mean the following:

    + : included by the combine algorithm
    # : backup (more than tos maxclock sources)
    ' ': (a space) discarded as not valid (TEST10-TEST13)
    x : discarded by intersection algorithm
    . : discarded by table overflow (not used)
    - : discarded by the cluster algorithm

    In our case, the servers above 3 are being discarded with the - sign, i.e., by the cluster algorithm.

    From documentation:
    minclock minclock
    Specify the number of servers used by the clustering algorithm as the minimum to include on the candidate list. The default is 3. This is also the number of servers to be averaged by the combining algorithm

    So from the above, I understand that I need to increase minclock from 3 to 6. Is this correct?

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  • From rcheaito via questions Mailing List@21:1/5 to All on Tue Feb 18 21:38:00 2025
    I changed the minclock on my system from 3 to 6 and looks this solves the
    issue of discarding the servers above 3.

    For the second issue, using the 'tos orphan 10 orphanwait 0' did not help. If anyone has other ideas, please let me know.

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  • From rcheaito via questions Mailing List@21:1/5 to All on Wed Feb 19 22:02:00 2025
    Yes, in theory I should not bother about this NTP behavior as this is after
    all controlled by the selection algorithm based on quality of communication with the server, precision,....etc. However, what made me follow through this issue mainly this:

    We allow user to configure up to 5 time sources on our system, and so if all 5 time servers are supposedly good, then the expectation is that one of them
    will be selected as the system peer and the remaining ones as backup. Not having this behavior will create confusion and raise questions. I understand that the system peer may change as NTP polls the servers, but still one will
    be selected as system peer and the remaining will be as backup (of course assuming all 5 are still considered as good time sources per the selection algorithm!).

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  • From rcheaito via questions Mailing List@21:1/5 to All on Fri Feb 21 00:23:00 2025
    When we have more than 3 servers configured (5 in our case), increasing the minclock from 3 to 6 should help keep all the 5 survivors by the cluster algorithm and terminate the pruning rounds faster, based on my understanding
    of the following snippets from documentation. And so this should lead to tagging the additional survivors in ntpq with a '+' sign instead of '-' sign
    as the additional survivors won't be discarded (as they are no longer pruned). Correct?

    From Documentation:
    The cluster algorithm operates in a series of rounds. The rounds are continued until a specified termination condition is met.
    At each round the remaining entries on the list represent the survivors of
    that round. If the candidate to be pruned is preemptable and the number of candidates is greater than the maxclock threshold, the association is demobilized.
    Further pruning is subject to the following termination conditions, but no associations will be automatically demobilized.
    The termination condition has two parts. First, if the number of survivors is not greater than the minclock threshold set by the minclock option of the tos command, the pruning process terminates.

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  • From rcheaito via questions Mailing List@21:1/5 to All on Fri Feb 21 21:53:00 2025
    I can say we are focusing more on the count of '+' and '-' signs. We may obviously be so paranoid by this, however the concern raised is that with 2 servers out of 5 showing as discarded ('-' sign) almost all the time, our clients will have questions raised when they know that those discarded servers are working fine with other boxes (with '*' or '+' sign).

    I did not run any statistical tests with those servers.

    From the different answers I got, increasing the minclock helps replace the '-' signs with the '+' signs against those previously discarded servers, but
    it may make our client more fragile. So, what I take from all those discussions that we better keep the minclock as 3 and then just document this behavior as expected!

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