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From Paul Loy <ketera...@gmail.com>
Subject Re: host clocks
Date Mon, 25 Jul 2011 13:03:30 GMT
we don't have those guarantees on EC2. Networks can fluctuate wildly.

On Mon, Jul 25, 2011 at 2:00 PM, zGreenfelder <zgreenfelder@gmail.com>wrote:

>
>
> On Mon, Jul 25, 2011 at 8:51 AM, Paul Loy <keteracel@gmail.com> wrote:
>
>> As I understand it, this will not quarantee that they are millisecond
>> accurate which is what you need for Cassandra to use the correct commit.
>> We've seen problems in production and had to rearchitect parts of the system
>> due to this even though all servers are NTP synched.
>>
>> http://www.endruntechnologies.com/faq.htm#How_accurate_is
>>
>>
>>
> Perhaps you'd do well to do some more intensive NTP configuration.
> Something like:
>
> outside server(s)  <--- 2 local NTP machines (time[01].mydomain) <---- X
> number of cassandra servers over lan
>
> assuming your lan is speedy enough, you should be able to get to the .5 MS
> range of sameness (which might still be 100MS off 'real' time, but I don't
> think you'd really care about that).
>
> it might even be worth creating your own NTP LAN that connects all the
> machines on an interface separate from Data & Management.
>
>
> --
> Even the Magic 8 ball has an opinion on email clients: Outlook not so good.
>



-- 
---------------------------------------------
Paul Loy
paul@keteracel.com
http://uk.linkedin.com/in/paulloy

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