Jason Pyeron wrote:
>
>
>> -----Original Message-----
>> From: centos-boun...@centos.org
>> [mailto:centos-boun...@centos.org] On Behalf Of Warren Young
>> Sent: Thursday, August 12, 2010 17:41
>> To: CentOS mailing list
>> Subject: Re: [CentOS] Date drift and ntpd
>>
>> On 8/12/2010 5:07 AM, Jason Pyeron wrote:
>>> [r...@devserver21 ~]# cat /etc/ntp.conf | grep -v ^# | grep -v ^$
>>> restrict default nomodify notrap noquery restrict 127.0.0.1 server
>>> 192.168.1.67 server 192.168.1.66 server 192.168.1.65
>> Some HOWTOs tell you that more time servers is better, on a
>> standard knee-jerk redundancy theory, but they're ignoring two things.
>>
>> First, you already have a fallback: the system's built-in
>> clock. It's perfectly fine to run on that while you ride out
>> your time server's downtime.
>>
>> Second, ntpd, internally, is built on a phase-locked loop,
>> which is supposed to stabilize its time corrections in the
>> face of jitter and other bad things out in the real world.
>> Like anything based on a negative feedback loop, however, it
>> can be destablized with certain inputs. Giving ntpd two or
>> more servers is a pretty good way to destabilize its PLL in
>> the real, non-ideal world we find on the modern Internet.
>>
>> To anyone considering flaming me, please read this first:
>>
>> http://queue.acm.org/detail.cfm?id=1773943
>>
>> At minimum, read the section "One server is enough". The bit
>> on PLLs about halfway down is also directly relevant.
>
> Okay, I only have one timeserver, but the ntp clients cowardly refuse to use
> less than 3. Back to the man page...
One server should be fine - you must have something else wrong, like your
authoritative server not being a low stratum number - or not convinced itself
that its time is correct.
--
Les Mikesell
lesmikes...@gmail.com
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