[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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