[ntp:questions] Time steping regardless of "-x" slew only option

Richard B. Gilbert rgilbert88 at comcast.net
Sat Jun 23 14:07:41 UTC 2007

vwvr6vw wrote:
> I am using the xntpd daemon with the AIX OS.  From what I have read,
> the use of the "-x" option should cause steps steps less than 3
> seconds to be slew'ed instead of step'ed.  However, I am seeing steps
> that are less than 3 seconds and show no pattern(anywhere from 0.1
> seconds to 1.7 seconds).  The only thing I can figure is that since
> ntp is selecting a different server to sync to, it does not follow the
> slew only logic that should be applied by the use of the "-x" option?
> i.e. if I only had one server defined in my config file and it
> stepped, I would not have a problem, but if I have two servers that
> are out of sync, then I could see a steps on my processor as it ping
> pongs back and forth between the two.

If you are using servers that differ from each other by "from 0.1. to 
1.7 seconds" you have made a VERY poor choice of servers!  In principle, 
servers should all have identical time; in practice they can and do 
differ by as much as ten milliseconds.  If two servers differ by more 
than that, something is wrong with at least one of the servers or your 
network connection to at least one of them.

The ntpd daemon should not be stepping at all unless something is badly 
broken somewhere.  The only exception is at startup.  If you use the -g 
option ntpd will set the clock uncondtionally (step) and then adjust the 
clock frequency as needed to keep the clock in synch with UTC.

Some Linux and Windows systems have been known to step frequently; this 
is due to loss of clock interrupts during heavy disk activity.

More information about the questions mailing list