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

Brad Knowles brad at stop.mail-abuse.org
Tue Feb 8 10:23:20 UTC 2005


At 10:05 AM +0000 2005-02-08, You have no need to know wrote:

>  I tried it by doing a 'ntp -n -c pe' and putting the resulting 16 IPs in
>  "ntpdate -d ..."
>
>  The first run took ~19 secs, most of which was *reverse* lookups of all
>  the IPs.
>
>  The following 3 runs each took between 3 and 4 secs.

	Listing four servers by IP address and making use of iburst, 
Steve has demonstrated that you can reliably get initial startup of 
ntpd in seven seconds.  Listing six servers by IP address and using 
iburst, along with Dr. Mills' recommendation of "tos minclock 4 
minsane 4", Steve has shown that you can get startup in eleven 
seconds.

	In my own testing, I've demonstrated that listing nine servers by 
host name (not IP address), with a good local nameserver running on 
the same machine, along with using iburst, you can get startup in 
eight seconds once the DNS cache is primed, which worsens to twenty 
seconds when the DNS cache is empty.

	But if seven seconds still isn't fast enough, see 
<https://ntp.isc.org/bin/view/Support/StartingNTP4#Section_6.1.4.4.>.


	As far as I'm concerned, seven to eight seconds is more than fast 
enough all for all situations I can think of, including the financial 
industry where you might be losing $50 million per second of 
downtime, or military applications.

	However, if you absolutely, positively, must have initial ntpd 
startup in less time than that, otherwise you will die the most 
horrible and painful possible death, other options are documented 
that can get your startup down as low as three seconds.

	If that's not fast enough for you, then you might as well give up hope.

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.



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