[ntp:questions] chrony as a server

Rob nomail at example.com
Sat Feb 21 17:56:52 UTC 2015


Brian Inglis <Brian.Inglis at SystematicSw.ab.ca> wrote:
> On 2015-02-21 01:00, Rob wrote:
>> 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 10:05:45AM +0000, Rob wrote:
>>>>>> We have systems in places that are not temperature controlled and then
>>>>>> chrony is much better.  I am looking for the best way to find the
>>>>>> values to use in the tempcomp configuration directive.
>>>>>
>>>>> What resolution does the sensor have? Don't expect good results
>>>>> with 1C or 0.5C resolution that sensors on mainboards typically have.
>>>>
>>>> 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.
>>>
>>> It is of course the temperature of the crystal itself that is important.
>>> Ie, the room temp could be constant and the computer varies in its
>>> workload and thus its internal temperature. Unfortunately temp sensors
>>> on the crystal are rare in commodity computers.
>>
>> I am not looking for a precise crystal temperature but for a ballpark
>> value that will compensate for the quick temperature swings that occur
>> when this system (which is in an unheated glasshouse) quickly warms up
>> when the sun rises, and cools down when the sun sets.
>>
>> In ntpd these events result in offset swings that are the derivative
>> of the temperature.   In chrony the swings are smaller, but it may be
>> deceptive because I have not yet found a completely satisfactory way
>> of gathering an "average offset" that is similar to the offset value
>> in ntpq -c rv.
>
> Hi Rob,
> If the systems can run x86/x64 Linux with Mono and WinForms or Windows
> with .NET 2+ then OpenHardwareMonitor may be able to log the system
> sensors.
> For Linux see if lm_sensors/sensord/sensors/sensors-detect are available
> on or for your system and look for data in:
> /proc/acpi/thermal_zone/
> /sys/bus/platform/devices/*temp*/
> /sys/class/hwmon/hwmon[0-9]*/
> /sys/class/thermal/{thermal_zone,cooling_device}[0-9]*/
> Once you have the data, you may want to try weighted or windowed incremental
> RMS values of temperature and frequency drift to see if they can be correlated.

I know how to access the sensors but I have not yet decided which sensor
is best to use, and how to calibrate the chrony configuration to it.

But even without the sensor input the offset is already much smaller than
with ntpd.



More information about the questions mailing list