[ntp:questions] help for Ntp architecture

Charles Swiger cswiger at mac.com
Tue Jul 9 18:09:50 UTC 2013


Hi--

On Jul 9, 2013, at 10:49 AM, Vuilmet Nicolas <nicolas.vuilmet at laposte.net> wrote:
> Sorry display schemas is bad.
> Retry

Indeed yes, your diagrams came through better this time.

> Le 08/07/2013 10:39, nicolas.vuilmet at laposte.net a écrit :
>> Hi,
>> 
>> I have a NTP architecture synchronize hundreds of ntp clients.
>> But i know my architecture is bad.
>> 
>> I have 3 time sources (1 GPS and 2 separate radio)
>> Each on source is deliver by only one NTP server (stratum 1).
>> All clients have in their configuration these three time servers of stratum 1.
>> Currently, a source is in maintenance. Its server is now on stratum 12.
>> All NTP clients see one of three servers in stratum 12.

You might (and probably should) configure your stratum-1 servers to be peers
of each other.  That way, they will continue to keep good time even if their
reference clock goes away, and they will provide time to your clients as
stratum-2 rather than stratum-12.

[ ... ]
>> I want to improve this architecture.
>> I think add NTP servers to create a stratum 2.
>> All NTP servers in stratum 2 synchronize across all stratum 1 servers.
>> May be also on them?
>> How many stratum 2 servers? tow minimum for high availability, 3 for total security but is it better have more?
>> In the end, all clients synchronize only the stratum 2 servers.

At least 4 timeservers is preferred, due to the way the clock selection algorithm works.

If you have tens of thousands of clients, then creating a tier of stratum-2 servers as
you've suggested is a sensible approach.  If you have fewer clients, then there's
really no requirement to add the stratum-2 tier, because your existing three stratum-1s
ought to be fine handling requests from less than 10K clients directly.

>> Finally, do you have tips on the hardware configuration of the stratum 2 servers? Are there an essential element? (CPU, network, disk.....)
>> I read an old server can be enough, but its good for my case? NTP architecture with many clients?

ntpd requires good networking, but minimal CPU, RAM, and involves no disk I/O-- well, unless you want to log peerstats or the like.

As for "good networking", that means good handling of near minimum-size packets with minimal latency, not lots of bandwidth.
Disable gigabit NIC interrupt coalescing if you can; older 10/100 ethernet NICs actually tend to work better for NTP.

Regards,
-- 
-Chuck



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