[ntp:questions] two machines syncing to the same master - hardware issues?

matthew.garman at gmail.com matthew.garman at gmail.com
Thu May 30 18:18:05 UTC 2013

I have two servers in the same physical location that are syncing to the same two NTP servers.  My understanding is that these NTP servers are in the same building as my servers, and we are connected via an in-building connection.  In other words, network jitter should be reasonably low (at least compared to the Internet, for example).

My two machines are somewhat different: "oldbox" is running NTP 4.2.2 as ships with RedHat 5.7; "newbox" is running NTP 4.2.4 as ships with RedHat 6.3..

Oldbox has been used as our company's central NTP server for many years.  But the machine is not dedicated to this purpose: it performs other business functions that are erratic in nature.  So we procured newbox to act as a poor-man's dedicated NTP server.  In other words, newbox does nothing but NTP.

What we've found is that newbox generally has a much larger offset to its NTP peer, compared to oldbox.  Likewise, newbox's offset also varies much more over time.

I'm measuring the offset via "ntpdate -q <peer ntp server>"

I rebooted newbox yesterday, and it has taken about 20 hours for newbox's offset to be in line with oldbox's.  And based on observation, I'm not so sure it will stay this way.

Is it possible there is a hardware problem with newbox?  I don't really understand NTP well enough to know where to start looking.

I guess a related question is, what kind of offset can I realistically expect in such a situation?  It seems like on oldbox the offset is consistently under 100 microseconds.


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