[ntp:questions] NTP servers redundancy

Richard B. Gilbert rgilbert88 at comcast.net
Tue Jan 19 16:35:18 UTC 2010

pc wrote:
> Jean,
> It's already been said (and others may say it again) that an NTP
> configuration with
> two servers is generally considered bad. That's true in the sense that
> a
> two-server setup won't give you better time than a single-server
> setup,
> and may indeed give you slightly worse time; you would have to do some
> testing to see if that is an issue for you. In many cases, it's
> sufficient
> if the time is accurate to plus/minus a second or two, and your setup
> should certainly achieve that. Using two (or more) servers is a good
> idea for achieving redundancy in case a server fails.
> Paul

The fundamental problem with two servers is this: which one do you 
believe when the two differ?  You know that at least one of the two must 
be wrong but it's impossible to determine WHICH one!

Three servers can degenerate too easily to the two server case.  That's 
why four are considered the minimum for a reliable configuration.

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