Hi, We have a little over 100 servers, almost all running CentOS 5.7. Virtually all are Dell servers, generally a mix of 1950s, R610s, and R410s. We use NTP and/or PTP to sync their clocks. One phenomenon we've noticed is that (1) on reboot, the clocks are all greatly out of sync, and (2) if the PTP or NTP process is stopped, the clocks start drifting very quickly. If it was isolated to one or two servers, I'd dismiss the issue. I also had this problem under CentOS 4. I suspect something is mis-configured, because I can't imagine the hardware clock on ALL these servers is *that* bad. Anyone else dealt with anything similar? Thanks! Matt
On Tue, 2013-01-22 at 21:16 -0600, Matt Garman wrote:> Hi, > > We have a little over 100 servers, almost all running CentOS 5.7. > Virtually all are Dell servers, generally a mix of 1950s, R610s, and > R410s. > > We use NTP and/or PTP to sync their clocks. One phenomenon we've > noticed is that (1) on reboot, the clocks are all greatly out of sync, > and (2) if the PTP or NTP process is stopped, the clocks start > drifting very quickly. > > If it was isolated to one or two servers, I'd dismiss the issue. I > also had this problem under CentOS 4. > > I suspect something is mis-configured, because I can't imagine the > hardware clock on ALL these servers is *that* bad.Well -- in my experience ( 15+ years with RH variants of Linux, and ~25 with various Unix flavors ) they CAN be that bad -- especially with some of the "economy" chipsets used with the Intel architecture. It gets worse when you have a CMOS battery that's getting old and weak. The clock may default back to its initial value, or it might just run slow. Some folks might consider this a "brute force" approach, but I keep it simple and just reset the hardware clock once a week via cron. I prefer to do it in the wee hours, shortly before the weekly cron jobs run on Sunday morning. Put something like this in root's crontab. 3 3 * * 0 /sbin/hwclock --systohc For the gory details, refer to the man page for "hwclock" and it will tell all.> > Anyone else dealt with anything similar? > > Thanks! > Matt > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos-- Ron Loftin reloftin at twcny.rr.com "God, root, what is difference ?" Piter from UserFriendly
From: Matt Garman <matthew.garman at gmail.com>> I suspect something is mis-configured, because I can't imagine the > hardware clock on ALL these servers is *that* bad.Tried SYNC_HWCLOCK=yes in /etc/sysconfig/ntpd? JD
On Jan 22, 2013, at 8:16 PM, Matt Garman wrote:> Hi, > > We have a little over 100 servers, almost all running CentOS 5.7. > Virtually all are Dell servers, generally a mix of 1950s, R610s, and > R410s. > > We use NTP and/or PTP to sync their clocks. One phenomenon we've > noticed is that (1) on reboot, the clocks are all greatly out of sync, > and (2) if the PTP or NTP process is stopped, the clocks start > drifting very quickly. > > If it was isolated to one or two servers, I'd dismiss the issue. I > also had this problem under CentOS 4. > > I suspect something is mis-configured, because I can't imagine the > hardware clock on ALL these servers is *that* bad. > > Anyone else dealt with anything similar?---- pretty much everyone deals with this issue in one way or another. You don't actually show us your ntp.conf but generally, I would recommend that you make this the very first line of ntp.conf: tinker panic 0 Craig