linux-kernel - Re: PROBLEM: Hardware clock instable

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Date:	Wed, 4 Jun 2008 16:38:24 +0200
From:	"Bart Van Assche" <bart.vanassche@...il.com>
To:	Lkm <lkm@...-linux.com>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: PROBLEM: Hardware clock instable

On Wed, Jun 4, 2008 at 4:22 PM, Lkm <lkm@...-linux.com> wrote:
> Le Wednesday 04 June 2008 15:40:49 Bart Van AsscI de, vous avez écrit :
>> The reason I asked for the ntpd logs is that I'm still not sure
>> whether there is a hardware problem.
>
> In fact i'm wondering too .... But we have so many server with the same
> problem...
...
> 26 Feb 11:25:12 ntpd[2422]: time reset -0.492486 s
> I Don't know if we have rebooted the server this day..

A "time reset" can happen for one of three reasons:
* as a startup phenomenon (ntpd's frequency estimate is still converging).
* because of a step in the reference clock.
* because of instability of the hardware clock. Personally I have not
yet seen this.

>> And can you also post the
>> output of ntpq -pn ?
>>
> ntpq -pn
>     remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> +192.168.0.150   195.220.194.193  3 u  531 1024  377    1.398    0.606   0.402
> *192.168.0.151   194.2.0.28       3 u  399 1024  377    0.554    0.426   0.172

This data looks normal -- both time servers have the same stratum,
reachability == 0377, delay and offset are below 5ms, and jitter is
below 1ms.

So I suggest that you observe the ntp logs for a few days and check
whether the ntp daemon logs any error messages.

Bart.
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