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From Dor Laor <...@scylladb.com>
Subject Re: Amazon Time Sync Service + ntpd vs chrony
Date Fri, 09 Mar 2018 02:39:43 GMT
Agree! When using client timestamp, NTP should be running on them as well.


On Thu, Mar 8, 2018 at 6:24 PM, Jeff Jirsa <jjirsa@gmail.com> wrote:

> Clients can race (and go backward), so the more computer answer tends to
> be to use LWT/CAS to guarantee state if you have a data model where it
> matters.
>
> --
> Jeff Jirsa
>
>
> On Mar 8, 2018, at 6:18 PM, Dor Laor <dor@scylladb.com> wrote:
>
> While NTP on the servers is important, make sure that you use client
> timestamps and
> not server. Since the last write wins, the data generator should be the
> one setting its timestamp.
>
> On Thu, Mar 8, 2018 at 2:12 PM, Ben Slater <ben.slater@instaclustr.com>
> wrote:
>
>> 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 https://www.instaclustr.c
>> om/apache-cassandra-synchronization/ which references some really good
>> and detailed posts from logentries.com on the potential issues).
>>
>> Cheers
>> Ben
>>
>> On Fri, 9 Mar 2018 at 02:07 Michael Shuler <michael@pbandjelly.org>
>> wrote:
>>
>>> 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,
>>> Michael
>>>
>>> On 03/08/2018 04:15 AM, Kyrylo Lebediev wrote:
>>> > Hi!
>>> >
>>> > Recently Amazon announced launch of Amazon Time Sync Service
>>> > (https://aws.amazon.com/blogs/aws/keeping-time-with-amazon-t
>>> ime-sync-service/)
>>> > and now it's AWS-recommended way for time sync on EC2 instances
>>> > (https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time.html).
>>> > 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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>>> --
>>
>>
>> *Ben Slater*
>>
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