[ntp:questions] Re: ntpd, boot time, and hot plugging

Tom Smith smith at cag.lkg.hp.com
Tue Feb 8 22:09:06 UTC 2005


Tom Smith wrote:
 > [snip]
> # time ntpdate -b [3 servers]
>  5 Feb 22:58:12 ntpdate[234803]: step time server [IP] offset -0.000136 sec
> 
> real    0m0.71s [you'll recall that with all the above servers, including
> user    0m0.00s  the one that's down, this still took only 6.73 seconds]
> sys     0m0.00s
> 
> # time ntpd -gq -c ntp.boot [same 3 servers, iburst minpoll 4]
> ntpd: time slew 0.001556s
> 
> real    0m41.01s
> user    0m0.06s
> sys     0m0.60s
> 
> # time ntpd -gq -c ntp.boot [same 3 servers, iburst minpoll 1]
> ntpd: time slew 0.002653s
> 
> real    0m37.00s
> user    0m0.10s
> sys     0m0.56s

As it turns out, this happened to have been using V4.1.1. The 4.2.0
build on this system was defective and had been moved out of the way.

Retested identically with 4.2.0:

# cat /etc/ntp.drift
-2.157

# time ntpdate -b [3 servers]
Looking for host [name] and service ntp
host found : [name]
Looking for host [name] and service ntp
host found : [name]
Looking for host [name] and service ntp
host found : [name]
  8 Feb 16:47:53 ntpdate[488600]: step time server [IP] offset -0.000395 sec

real    0m0.71s
user    0m0.00s
sys     0m0.01s

# time ntpd -gq -c ntp.boot [same 3 servers, iburst minpoll 1]
ntpd: time slew -0.000711s

real    0m7.13s
user    0m0.00s
sys     0m0.03s

So, without DNS in the way, 4.2.0 gets it from a 50:1 difference to a
10:1 difference. A big improvement, to be sure, but this is only with
3 servers (none of them the local clock, of course).

-Tom



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