> -----Original Message-----
> From: centos-bounces@xxxxxxxxxx
> [mailto:centos-bounces@xxxxxxxxxx] On Behalf Of Warren Young
> Sent: Thursday, August 12, 2010 17:41
> To: CentOS mailing list
> Subject: Re: Date drift and ntpd
>
> On 8/12/2010 5:07 AM, Jason Pyeron wrote:
> >
> > [root@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...
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