[ntp:questions] chrony as a server

Rob nomail at example.com
Sat Feb 21 07:56:50 UTC 2015


William Unruh <unruh at invalid.ca> wrote:
> On 2015-02-19, Rob <nomail at example.com> wrote:
>> Miroslav Lichvar <mlichvar at redhat.com> wrote:
>>> On Thu, Feb 19, 2015 at 12:48:46PM +0000, Rob wrote:
>>>> I am still finding out what sensor is best to use, we do have a room
>>>> temperature sensor that has .1C resolution and is readable via snmp,
>>>> and there are the usual sensors for board- and inlet air temperature.
>>>> (and of course CPU temperature)
>>>> 
>>>> It does not matter if it is only a course indication, the room temperature
>>>> varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not
>>>> bad relative to that.
>>>
>>> In my tests using a sensor with 1C resolution it was barely useful
>>> with NTP sources and 1024s polling interval. If the sensitivity is
>>> around 0.1 ppm per degree, 1C resolution means the compensation
>>> jumping the frequency in 0.1ppm steps. That's a lot, especially if you
>>> compare it to the tracking skew with a refclock.
>>
>> Ok but of course we are using PPS and a 16 second polling interval.
>> (or maybe the PPS refclock polls even faster although it displays 4 as
>> the poll interval indicator)
>
> The shm refclock will get one pulse per second, and then average the
> offsets over a 16 sec period after getting rid of the outliers.

I am not using the SHM refclock in those systems.



More information about the questions mailing list