[ntp:questions] ntp server pool advice

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Tue Dec 27 13:00:17 UTC 2011


ben slimup wrote:
>
> Thank Danny and Dave,
>
> Your explanations are nice and clear.
>
> so in that case does it means that ntp protocol cannot be load
> balanced at all??

Rather the opposite!

ntp is by design load-balanced: You enter a bunch of servers for each 
client, the client will then monitor each server and decide which is 
currently performing best, sync to this one, while keeping the rest as 
backup/sanity check.
>
> are there any ways to provide load balancing without disturbing ntp
> roundtrip proccess?

If you have more than 4-6 servers, then you can use round-robin DNS to 
give each client a unique set of server IPs. Up to this number of 
servers, which is what you seem to be intending, you should simply let 
each client poll every server.

The polling interval will quickly back off from the starting 64s, most 
client/server combinations will end up at the maximum (1024s) poll interval.
>
> since i have gotten a lot of devices here , i made a simple design
> that all servers have their own public ip adresses. but my concern
> is that design is  my clients can handle only 4 ntp servers, and to
> fit the requirement of 1million synch per poll, i will need 8 servers
> at least.. do you guys have any design idea that can handle such
> traffic after blackout for example?

If you configure minpoll 7, then you will never poll more often than 
every 128 s, right?

With 1M clients, all talking to all servers (or at least all talking to 
the currently best server), that corresponds to less than 8000 
requests/second.

8000 is safely below the 10K limit you have stated that each of your 
intended ntp servers can handle.

However, I would instead leave the default (64 s/minpoll 6) minimum poll 
interval, but use round-robin DNS to let each client get a random group 
of 4 out of the 6 or 8 total servers.
>
> your help is really appreciated

You still haven't told us what you want to do, i.e. what sort of system 
are you setting up?

Terje

-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"



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