[ntp:questions] Synchronizing to LOCAL(0): Startup time
Richard B. Gilbert
rgilbert88 at comcast.net
Mon Oct 15 16:43:29 UTC 2007
Bert Gøtterup Petersen wrote:
> Thanks for the reply, and for the hint toward the ntp-dev version. It does
> indeed synch to "the local clock" within 1s; GREAT!!!
> In you answer and in several of the other aswers I got, this orphan mode is
> mentioned. I am not sure I fully get it yet.
> Let me try to answer like this:
> If I have two server products (s1 and s2) and one client (c1), and I want to
> run them as an 'isolated island' yet locally synchronized (very well).
Depending on how small a difference between server and client you call
"synchronized (very well)" you may need a hardware reference clock.
Even if you don't really care exactly what time it is, a reference clock
gives you an extremely stable reference to synchronize to. One
unsynchronized machine trying to synchronize with another such machine
can behave very much like one drunken driver trying to follow another.
With a GPS reference, and a "good" LAN, you can synchronize two machines
to within a few hundred microseconds.
"Orphan Mode" is a means of "synchronizing" a "time island" using what
is essentially a randomly selected server. The machines involved decide
among themselves who has the "best" clock. I have never tried it, or
needed to; I have a GPS reference! Perhaps someone who has tried it and
tested the closeness of synchronization can comment.
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