| Re: [chrony-users] Accuray statistical claims |
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On Mon, 10 Jul 2017, Miroslav Lichvar wrote:
On Sat, Jul 01, 2017 at 12:03:30AM +0300, Horia Muntean wrote:
....
If the answer in no, please explain. Any advice about how can this
(prove that a client's system clock is within a target from UTC) be
done only with NTP/chrony ? AFAIK if one wants to measure the accuracy
of a system, another more accurate system must be used (in my case
maybe installing a PPS card on the client then comparing its output
with the server's PPS output) but we can't afford to do this on each
client.
If you put such a card in then you would of course use it, not ntp, to
discipline the clock. However, you can run a single test bed in which you
connect one such more accurate clock to one of your clients to see what the
relation is between its chrony driven time and the more accurate time from the
PPS source (eg a gps puck).
This would of course not catch some sudden change in one of the intermediate
routers on your system which introduced a 10us delay in one of the paths and
not the other when the gps clock was not attached.
Not sure what you mean by prove? In a court of law? And what would the
consequences be of not having the time be sufficiently accurate? If high
enough then the cost of a say a gps attached to each client would be worth it.
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