On Fri, 23 Jun 2006, Richard B. Gilbert wrote:
Julien wrote:
Hello,
I'm requesting some advice here. I have a bunch of Linux servers
(around 20) to synchronize, and I'm planning to use NTP for it. Theses
[...]
Questions :
1/ do I need 3 reference clocks (GPS receivers...) for my 3 strate 1
servers ?
No. You can connect the signals from one refclock to three or more servers.
Connect the transmit data line from only one of the servers.
You may need to do some signal buffering since the typical RS232 output is
not designed to drive three inputs.
The reason for having multiple servers is that servers are somewhat
fragile. You might want to arrange to keep the servers physically far
apart (e.g., different buildings), in which case cheap GPS units will
probably cost less than the wiring to connect one server to multiple
servers.
Having only one refclock makes it a single point of failure. If it dies you
have nothing. Unless you cannot tolerate a failure, having three refclocks
and three servers seems to me to be overdoing it a little. Since you have
nothing now, it seems likely to me that you could survive a failure until you
could repair or replace the failing component.
The old Trimble at work sometimes stops providing time for a while --
could be a software bug. I'd worry that 3 identical GPS's could glitch at
the same time, so it makes sense to get a couple of the cheapest units and
one of the next cheapest. Maybe new units don't have glitches, but since
they are new nobody has tested them for 10+years.
--
George N. White III <[EMAIL PROTECTED]>
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