[ntp:questions] NTP servers redundancy

Richard B. Gilbert rgilbert88 at comcast.net
Tue Jan 19 17:26:20 UTC 2010

Rob wrote:
> Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
>> 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!
> This is not relevant when the two servers return the same time within
> the margin that one considers acceptable.

It would be wonderful if we could rely on two servers always agreeing!

The last "NTP Survey"  (google for it) found at least one server that 
responded with the wrong year!

> So when you have two servers that each are synchronized to the same
> GPS PPS clock, there should be no problem.  They return the same time
> or no response at all (when down) and the clients will lock on either
> of them without problem.
And when that "GPS PPS Clock" fails?  It should not but that's not the 
same as cannot!

> When a server returns the wrong time and still says it is synchronized,
> there is a software bug.  This you aren't going to solve with as many
> servers as you like (all setup the same way).  Then you would need to
> run many servers with different software versions, different OS, different
> hardware, etc.
> Probably more trouble than the problem is worth.

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