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From Kyrylo Lebediev <>
Subject Re: Amazon Time Sync Service + ntpd vs chrony
Date Fri, 09 Mar 2018 11:53:49 GMT
Thank you to all who replied so far,  thank you Ben for the links you provided!

From: Ben Slater <>
Sent: Friday, March 9, 2018 12:12:09 AM
Subject: Re: Amazon Time Sync Service + ntpd vs chrony

It is important to make sure you are using the same NTP servers across your cluster - we used
to see relatively frequent NTP issues across our fleet using default/public NTP servers until
(back in 2015) we implemented our own NTP pool (see
which references some really good and detailed posts from<>
on the potential issues).


On Fri, 9 Mar 2018 at 02:07 Michael Shuler <<>>
As long as your nodes are syncing time using the same method, that
should be good. Don't mix daemons, however, since they may sync from
different sources. Whether you use ntpd, openntp, ntpsec, chrony isn't
really important, since they are all just background daemons to sync the
system clock. There is nothing Cassandra-specific.

Kind regards,

On 03/08/2018 04:15 AM, Kyrylo Lebediev wrote:
> Hi!
> Recently Amazon announced launch of Amazon Time Sync Service
> (
> and now it's AWS-recommended way for time sync on EC2 instances
> (
> It's stated there that chrony is faster / more precise than ntpd.
> Nothing to say correct time sync configuration is very important for any
> C* setup.
> Does anybody have positive experience using crony, Amazon Time Sync
> Service with Cassandra and/or combination of them?
> Any concerns regarding chrony + Amazon Time Sync Service + Cassandra?
> Are there any chrony best-practices/custom settings for C* setups?
> Thanks,
> Kyrill

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