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From Anuj Wadehra <anujw_2...@yahoo.co.in>
Subject Re: Configure NTP for Cassandra
Date Tue, 13 Dec 2016 18:55:43 GMT
Thanks for the NTP link. Most of us are Cassandra users and must be using NTP (or other time
synchronization methods) for ensuring relative time synchronization in our Cassandra clusters.
I hope there are people on the mailing list who can answer these questions with respect to
Cassandra. 
There is just one detailed blog on NTP best practices for Cassandra and I think answering
these questions is important rather than just creating an internal NTP pool with recommended
settings.

Thanks
Anuj 
 
  On Wed, 14 Dec, 2016 at 12:07 AM, Jim Witschey<jim.witschey@datastax.com> wrote: 
 You might find more NTP experts on the NTP questions mailing list:
http://lists.ntp.org/listinfo/questions

On Tue, Dec 13, 2016 at 1:25 PM, Anuj Wadehra <anujw_2003@yahoo.co.in> wrote:
> Any NTP experts willing to take up these questions?
>
> Thanks
> Anuj
>
> On Sun, 27 Nov, 2016 at 12:52 AM, Anuj Wadehra
> <anujw_2003@yahoo.co.in> wrote:
> Hi,
>
> One popular NTP setup recommended for Cassandra users is described at
> Thankshttps://blog.logentries.com/2014/03/synchronizing-clocks-in-a-cassandra-cluster-pt-2-solutions/
> .
>
> Summary of article is:
> Setup recommends a dedicated pool of internal NTP servers which are
> associated as peers to provide a HA NTP service. Cassandra nodes sync to
> this dedicated pool but define one internal NTP server as preferred server
> to ensure relative clock synchronization. Internal NTP servers sync to
> external NTP servers.
>
> My questions:
>
> 1. If my ISP provider is providing me a pool of reliable NTP servers, should
> I setup my own internal servers anyway or can I sync Cassandra nodes
> directly to the ISP provided servers and select one of the servers as
> preferred for relative clock synchronization?
>
>
> I agree. If you have to rely on public NTP pool which selects random servers
> for sync, having an internal NTP server pool is justified for getting tight
> relative sync as described in the blog
>
> 2. As per my understanding, peer association is ONLY for backup scenario .
> If a peer loses time synchronization source, then other peers can be used
> for time synchronization. Thus providing a HA service. But when everything
> is ok (happy path), does defining NTP servers synced from different sources
> as peers lead them to converge time as mentioned in some forums?
>
> e.g. if A and B are peers and thier times are 9:00:00 and 9:00:10 after
> syncing with respective time sources, then will they converge their clocks
> as 9:00:05?
>
> I doubt the above claim regarding time converge. Also no formal doc says
> that. Comments?
>
>
> Thanks
> Anuj
>
  

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