On 8/12/2010 5:07 AM, Jason Pyeron wrote: > > [root at 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.