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From "J. Ryan Earl" <>
Subject Re: Multi-dc restart impact
Date Thu, 10 Oct 2013 15:15:25 GMT
Are you doing QUORUM reads instead of LOCAL_QUORUM reads?

On Wed, Oct 9, 2013 at 7:41 PM, Chris Burroughs

> I have not been able to do the test with the 2nd cluster, but have been
> given a disturbing data point.  We had a disk slowly fail causing a
> significant performance degradation that was only resolved when the "sick"
> node was killed.
>  * Perf in DC w/ sick disk:**png?1<>
>  * perf in other DC:**png?1<>
> Not only was a single slow node able to cause an order of magnitude
> performance hit in a dc, but the other dc faired *worse*.
> On 09/18/2013 08:50 AM, Chris Burroughs wrote:
>> On 09/17/2013 04:44 PM, Robert Coli wrote:
>>> On Thu, Sep 5, 2013 at 6:14 AM, Chris Burroughs
>>> <>**wrote:
>>>  We have a 2 DC cluster running cassandra 1.2.9.  They are in actual
>>>> physically separate DCs on opposite coasts of the US, not just logical
>>>> ones.  The primary use of this cluster is CL.ONE reads out of a single
>>>> column family.  My expectation was that in such a scenario restarts
>>>> would
>>>> have minimal impact in the DC where the restart occurred, and no
>>>> impact in
>>>> the remote DC.
>>>> We are seeing instead that restarts in one DC have a dramatic impact on
>>>> performance in the other (let's call them DCs "A" and "B").
>>> Did you end up filing a JIRA on this, or some other outcome?
>>> =Rob
>> No.  I am currently in the process of taking a 2nd cluster from being
>> single to dual DC.  Once that is done I was going to repeat the test
>> with each cluster and gather as much information as reasonable.

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