[ntp:questions] Re: Toggling time sync between two servers

Richard B. Gilbert rgilbert88 at comcast.net
Sun Mar 26 20:13:06 UTC 2006


vwvr6vw wrote:

> Thanks for the replies.  I've recommended to my management that we
> abandon the third party software and instead purchase four independant
> NTP servers.  I think this is the most simplistic solution given our
> current problems, which are difficult to debug.  It is also a better
> solution.  I'm not sure they will go for it given the state of our
> project, but I will push for it.
> 

Depending on what you mean by "four independent NTP servers" you could 
be talking about a lot of money!  One server is sufficient for 
non-critical applications.  Everybody will stay in synch with it without 
problems.  The weaknesses are:
1. If the server has the wrong time, everybody has the wrong time. In 
some shops that's a problem, in others, not!
2. If the server fails, you are without a server.

If you must have the correct time, you need to configure each client 
with a minimum of four servers.  Those four servers can be existing 
machines.  Each one needs a source of time.  That source can be a 
hardware reference clock; e.g. a GPS timing receiver or a minimum of 
four internet servers.  If you use internet servers, each of your 
internal servers should have at least one unique external server or 
seven in all.

If you need really tight synchronization among the clients; e.g. 
everyone within ten microseconds, you pretty much have to have a GPS 
reference clock.  Few shops need synchronization that tight but you need 
to specify just what your needs are for: accuracy, tightness of 
synchronization, and reliability before you can design a good solution.




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