[CentOS] Date drift and ntpd

Thu Aug 12 22:15:09 UTC 2010
John R Pierce <pierce at hogranch.com>

  On 08/12/10 2:51 PM, Warren Young wrote:
> Only one server on a given LAN should be running ntpd.  It's overkill
> for every machine to keep themselves synced with such a complex and
> fussy server.  All the others should just call ntpdate or msntp every
> hour or so as a cron job to keep their own time close to that of the LAN
> time server's.

I disagree.

Simply setting a systems time at fixed intervals will result in 
discontinuities in delta time measurements.  if the systems local clock 
is fast, a given time will occur twice, and a delta between two time 
readings could be negative.    if the clock is slow, a delta between two 
readings would jump by whatever correction.

I do think that having one NTP master server onsite which syncs either 
to a hardware clock (GPS etc), or to 1 to 3 external NTP servers, then 
having all the rest of your local servers sync to this one NTP master 
server is the correct architecture.    Once an ntpd synchs and 
stabilizes to its reference, its very low overhead.